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Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
1
TABLE OF CONTENTS
(A). Abstract .................................................................................................................................................................... 3
(B). List of Figures .......................................................................................................................................................... 4
1. Fundamentals of EMI/EMC ..................................................................................................................................... 6
What is EMI/EMC ....................................................................................................................................................... 7
Source of Electromagnetic Interference ................................................................................................................... 7
The three elements of an EMI problem .................................................................................................................... 8
Types of coupling in EMI ........................................................................................................................................... 9 Impedance coupling .............................................................................................................................................. 10 Inductive coupling ................................................................................................................................................ 11 Capacitive coupling ............................................................................................................................................... 11 Radiative coupling ................................................................................................................................................. 11 Crosstalk ................................................................................................................................................................. 12
Modes of coupling in EMI ........................................................................................................................................ 12
Differential Mode .................................................................................................................................................. 12 Common Mode ..................................................................................................................................................... 13
2. Medium and High frequency modeling of components ................................................................................... 14
Capacitors ................................................................................................................................................................... 15
Inductors ..................................................................................................................................................................... 16
Power diode with reverse recovery ......................................................................................................................... 18
Power MOSFET ......................................................................................................................................................... 21
3. Measurement of EMI in DC-DC converters ....................................................................................................... 29
What are DC-DC power converters ....................................................................................................................... 30
Fly-back converter ..................................................................................................................................................... 30
Basic topology of fly-back converter ....................................................................................................................... 31
Line Impedance Stabilization Network (LISN) ..................................................................................................... 32
Measurement of EMI ................................................................................................................................................ 35
4. EMI filter design for DC-DC converters ............................................................................................................. 43
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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Introduction ............................................................................................................................................................... 44
Topology of an EMI filter ......................................................................................................................................... 44
Basis of determining filter component values ....................................................................................................... 45
Common mode ...................................................................................................................................................... 45 Differential mode .................................................................................................................................................. 47
Software based EMI noise separation method ....................................................................................................... 48
Design procedure for EMI filter .............................................................................................................................. 49
Software implementation of EMI filter design ...................................................................................................... 51
SPICE verification of the designed EMI filter ........................................................................................................ 53
Comparison of results obtained with and without filter ...................................................................................... 62
5. Conclusion ................................................................................................................................................................. 63
6. References .................................................................................................................................................................. 64
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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ABSTRACT
The goal of this work was to simulate the Electromagnetic Interference (EMI) generated in a fly-back converter, design a filter based on the generated data and to study the EMI characteristics of the power converter after integration with the filter.
To achieve the designated goals, SPICE models of Power MOSFET and Power diode were improved to simulate the switching characteristics and the reverse recovery characteristics respectively. These improved models are then integrated in the fly-back converter and the EMI data is generated. Based on the data generated, a filter is designed and then integrated to the power converter. The EMI characteristics of the circuit are again generated and a significant improvement in the EMI characteristics is observed.
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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LIST OF FIGURES
S. No Figure Page 1. The three elements of an EMI problem 8 2. Possible modes of coupling in EMI 9 3. Impedance coupling between System A and System B 10 4. Avoiding common impedance between System A and System B 11 5. Differential mode noise 12 6. Common mode noise 13 7. Series R-L-C model for capacitor with parasitic effects 15 8. Impedance response of a series R-L-C model for capacitor 15 9. Impedance response of an ideal capacitor 16 10. Parallel R-L-C model for inductor with parasitic effects 17 11. Impedance response of a parallel R-L-C model for inductor 17 12. Impedance response of an ideal inductor 18 13. Reverse recovery current of a diode 18 14. Input voltage and Output current of a diode 20 15. Close-up view of the reverse recovery characteristic of diode 20 16. Test structure for the proposed MOSFET model 21 17. Internal schematic diagram of the proposed MOSFET model 22 18. Step response of gate-source voltage 27 19. Step response of drain-source voltage 28 20. Step response of drain current 28 21. Ideal fly-back converter schematics 31 22. Output characteristics of an ideal fly-back converter 32 23. Measurement setup for conducted EMI 33 24. Schematic of LISN 33 25. Impedance offered by LISN for the full frequency spectrum (10Hz to 100 MHz) 34 26. Impedance offered by LISN in the high frequency range (10kHz to 100MHz) 34 27. Circuit to measure EMI generated by fly-back converter (with parasitic and realistic
elements) 35
28. Output voltage of the fly-back converter with parasitic elements 39 29. Output voltage ripple 39 30. FFT of the output waveform 40 31. Frequency vs. live voltage (dBμV) 40 32. Frequency vs. neutral voltage (dBμV) 41 33. Common mode noise (in dBμV) 42 34. Differential mode noise (in dBμV) 42 35. Topology of an EMI filter 45 36. Common mode noise equivalent circuit 45 37. Differential mode noise equivalent circuit 45 38. Common mode noise equivalent circuit 46 39. Equivalent circuit of Fig. 38 if ZP >> ( ) and w(Lc + Ld/2) >> 25Ω 46
40. Equivalent circuit of Fig. 39 after applying reciprocity theorem 46 41. Filter attenuation for common-mode noise 46
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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42. Differential mode noise equivalent circuit 47 43. Equivalent circuit of Fig. 42 if ZCX1 >> 100Ω; ZCX2 >> ZP; and wLDM >> 100Ω 47 44. Equivalent circuit of Fig. 43 after applying reciprocity theorem 47 45. Filter attenuation for differential-mode noise 47 46. Circuit diagram for separation of conductive EMI signals 48 47. Flowchart of software based separation of conductive EMI signals 48 48. Design steps of the presented filter design 50 49. Developed MATLAB GUI for conducted EMI filter design 51 50. EMI filter results obtained for the fly-back converter 52 51. EMI filter using the data obtained by the GUI 53 52. Attenuation curve for the EMI filter designed 53 53. LISN followed by EMI filter and fly-back converter 54 54. Output voltage of the fly-back converter with LISN and EMI filter 58 55. Output voltage ripple with EMI filter 59 56. FFT of the output voltage with EMI filter 59 57. Frequency vs. live voltage with EMI filter (in dBμV) 60 58. Frequency vs. neutral voltage with EMI filter (in dBμV) 60 59. Common mode noise with EMI filter (in dBμV) 61 60. Differential mode noise with EMI filter (in dBμV) 61 61(A) Common mode noise without EMI filter 62 61(B) Common mode noise with EMI filter 62 62(A) Differential mode noise without EMI filter 62 62(B) Differential mode noise with EMI filter 62
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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1. Fundamentals of EMI/EMC
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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WHAT IS EMI/EMC
Electromagnetic Interference can be described as the degradation of a device or system caused by an electromagnetic disturbance. An electromagnetic disturbance is any phenomena, which may degrade the performance of a device, equipment or system, or adversely affect living or inert matter. An example of EMI affecting living matter is the current controversy regarding portable cellular telephones causing brain tumours.
Therefore, an electromagnetic disturbance can be an unwanted signal or even a change in the propagation medium itself. A change in the propagation medium can attenuate the signal and have a direct effect on the level of disturbance.
On the other hand, EMC (Electromagnetic Compatibility) can be described as the ability of different pieces of electrically operated equipment to work in close proximity to each other without causing any mutual interference. EMC therefore implies the ability of equipment to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to any other equipment in that environment. EMC is a twofold occurrence and consists of emissions and immunity.
First, EMC implies that the equipment will not generate unacceptable interference emission levels, which could cause interference; and second, EMC implies that the equipment’s intrinsic immunity levels are such that it can tolerate ambient levels of interference without degradation of performance.
Therefore, EMC means that a device must be capable of operating in all modes in the environment for which it was designed without degrading its own performance or that of any nearby equipment.
SOURCES OF ELECTROMAGNETIC INTERFERENCE
An electromagnetic environment can be described as the electromagnetic conditions existing at a given location. The EMI environment includes interference emanating from natural sources like lightning and atmospheric static to the various man-made sources of interference such as vacuum cleaners, washing machines, power tools, computers, cellular phones, mobile radios and even electronic toys.
Natural sources can be either terrestrial or extra-terrestrial in nature. Man-made sources include intentional or unintentional radiators. Within the scope of man-made noise sources, we can break it down even further into Inter-system interference and Intra-system interference. Inter-system interference is EMI in a system caused by an electromagnetic disturbance generated by another system; whereas Intra-system interference is self-generated EMI present in a system.
There is very little that can be done to prevent electromagnetic energy generated from natural interference sources. However, natural sources do not create that much of a problem except for perhaps, surges and spikes on power lines induced by lightning strikes. It is also very difficult to prevent EMI from intentional sources of electromagnetic energy. Cellular telephones and two-way radios are a major problem and can
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
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create havoc for example in hospital environments. It is therefore crucial that electronic equipment be made immune or less susceptible to environmental interference.
However, the major source of all interference is generated from unintentional manmade sources. This is due to the vast amount of electrical and electronic equipment in use.
THE THREE ELEMENTS OF AN EMI PROBLEM
There are three essential elements to any EMC problem. There must be an EMI source or an electromagnetic disturbance, a receptor or ”victim” that cannot function properly due to the electromagnetic phenomenon, and a path between them that allows the source to interfere with the receptor. Each of these three elements must be present at the same time in order to have an electromagnetic disturbance or EMI. Identifying at least two of these elements and eliminating or attenuating the interference from one of them can solve EMC problems.
Interference signals are established whenever electrons move. Therefore, any current flow may cause either direct coupling to other circuits or radiated fields, which may in turn couple unwanted signals into other circuits.
Their frequency, bandwidth and amplitude can characterize sources of interference. The propagation medium of EMI below 30 MHz tends to be mains-borne or conducted. The interference travels along the power cord or signal lines from the source to the receptor or victim circuit. The conducted interference is not easily attenuated over distance.
The radiated portion of EMI emissions is borne as an electromagnetic wave, propagating through the air or any other non-conducting media. Generally, the higher the EMI in the frequency spectrum, the more easily it will radiate. EMI and EMC are becoming more of a problem due to the trend to produce equipment in smaller packages operating at very high speeds and processing rates.
The use of higher speed switching logic increases emissions from printed circuit boards. Also the use of devices with low operating voltages and currents, packaged more closely together, increases the potential for intra-system interference and reduced immunity (increased susceptibility).
Coupling Path
Fig. 1- the three elements of an EMI problem
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Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
14
2. Medium and High frequency modelling of components
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15
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16
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allel R-L-C m
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17
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Reverse recooccurs whetransient rev
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ODE WITH
overy plays aen a forwardverse curren
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model availaaracteristics.
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Fig. 12
REVERSE R
an importantd conducting
nt to flow at h
ely used in cihe effects of cdiode. Thus,
o the no-con3.
Fig
able in SPIC. The SPICE
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2 – Impedan
RECOVERY
t role in the ag diode is t
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erse recoveryharge causes
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Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
19
Reverse recovery diode *reverse recovery Vin 1 0 pulse (-10 10 600n 0 0 600n 1200n) Rin 1 2 10 Xd1 2 0 40EPS08 .SUBCKT 40EPS08 A K D1 A K 40EPS08 .MODEL 40EPS08 d ( +IS=1e-15 RS=0.00426912 N=0.926332 EG=0.6 +XTI=0.5 BV=800 IBV=0.0001 CJO=1e-11 +VJ=0.7 M=0.5 FC=0.5 TT=1e-09 +KF=0 AF=1 ) .ENDS *reverse recovery .tran 1n 5600n 0 1n .probe
.end
Diode Model Parameters
Model Parameter Description Unit Value Specified IS Saturation current A 1E-15 RS Parasitic resistance Ohm 0.00426912 N Emission coefficient - 0.926332 EG Bandgap voltage (barrier height) eV 0.6 XTI IS temperature exponent - 0.5 BV Reverse breakdown knee voltage V 800 IBV Reverse breakdown knee current A 0.0001 CJO Zero-bias p-n capacitance F 1E-11 VJ p-n potential V 0.7 M p-n grading coefficient - 0.5 FC Forward-bias depletion capacitance coefficient - 0.5 TT Transit time Sec 1E-9 KF Flicker noise coefficient - 0 AF Flicker noise exponent - 1
Electromagn
etic Interfere
Fig
nce (EMI) and
Fig. 14
g. 15 – Close-
d filter design
4 – Input volt
up view of th
for SMPS
tage and Outp
he reverse rec
tput current o
overy charac
Centre fo
of diode
cteristics of di
or Airborne Sy
iode
ystems, DRDOO
20
Electromagn
POWER M
The commoit also has itthe drain-tolinearity of t
In this sectmentioned drain-sourcwhere it cor
etic Interfere
OSFET
on PSpice mts lacks for so-source resithe MOS cap
tion, a Poweparameters.
ce voltage, drrrectly predic
nce (EMI) and
odel for the some critical istance relatepacitor again
er MOSFET The chosen
rain current cts the EMI g
Fig. 16 –
d filter design
power MOSsimulating p
ed to the simnst applied vo
is modelled approach suand gate-sou
generated by
Test Structur
for SMPS
SFET devicesproblems. Th
mulation tempoltage.
taking intouccessfully reurce voltage
y the converte
re for the pro
is satisfyinghese lacks coperature and
account theeproduces th. The modeler.
oposed MOSF
Centre fo
g for most of onsist especiad in almost n
e non-lineare step respon is employed
FET model
or Airborne Sy
f the designerally in poor m
no-modelling
rity aspects onse characted in a fly-bac
ystems, DRDO
r’s needs butmodelling ofg of the non-
of the aboveristics of theck converter
O
21
t f -
e e r
Electromagn
The SPICE
POWER M .OPTION Vcc 1 0Vin 10 l1 1 2 r1 2 3 r2 10 1ls 13 0 Xm1 3 1
.subckt* * 10 = * ******** *------* PACKA
etic Interfere
Fig
macro-mode
MOSFET Mod
NS METHOD=
0 dc 50 0 pulse(0
51n 5
11 56 0 3n
11 13 mtp6
t mtp6n60/
Drain 20
**********
----------AGE INDUCT
nce (EMI) and
g. 17 – Interna
el code for th
del
=GEAR
10 0 20n
6n60/mc
mc 10 20 3
= Gate 30
**********
---------- TANCE
d filter design
al schematic
he above sho
20n 510n
30
= Source
**********
EXTERNAL
for SMPS
diagram of t
own schemati
4u)
***********
PARASITICS
the proposed
ic is as follow
**********
S --------
Centre fo
MOSFET mo
ws:
***********
-----------
or Airborne Sy
odel
**********
----------
ystems, DRDO
*****
-----
O
22
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
23
* LDRAIN 10 11 4.5e-09 LGATE 20 21 7.5e-09 LSOURCE 30 31 7.5e-09 * * RESISTANCES * RDRAIN1 4 11 RDRAIN 0.8036 RDRAIN2 4 5 RDRAIN 0.0084 RSOURCE 31 6 RSOURCE 0.02018 RDBODY 8 30 RDBODY 0.0135 * RGATE 21 2 5 * *-------------------------------------------------------------------------- * *--------------- CAPACITANCES AND BODY DIODE ------------------------------ * DBODY 8 11 DBODY DGD 3 11 DGD CGDMAX 2 3 2.7e-09 RGDMAX 2 3 1e+08 CGS 2 6 1.31e-09 * *-------------------------------------------------------------------------- * *----------------------- CORE MOSFET -------------------------------------- * M1 5 2 6 6 MAIN * *-------------------------------------------------------------------------- * .MODEL RDRAIN R( +TC1 = 0.008891 +TC2 = 3.056e-05) * .MODEL RSOURCE R( +TC1 = -0.003198 +TC2 = 2.60004e-05) * .MODEL RDBODY R( +TC1 = 0.003945 +TC2 = 9.54752e-06) * * .MODEL MAIN NMOS ( +LEVEL = 3 +VTO = 3.8 +KP = 13 +GAMMA = 2.6 +PHI = 0.6 +RD = 0 +RS = 0 +CBD = 0 +CBS = 0 +IS = 1e-14 +PB = 0.8 +CGSO = 0 +CGDO = 0 +CGBO = 0 +RSH = 0 +CJ = 0 +MJ = 0.5 +CJSW = 0 +MJSW = 0.33 +JS = 1e-14 +TOX = 1e-07 +NSUB = 1e+15
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
24
+NSS = 0 +NFS = 6.59e+11 +TPG = 1 +XJ = 0 +LD = 0 +UO = 600 +VMAX = 0 *+NEFF = 1 +KF = 0 +AF = 1 +FC = 0.5 +DELTA = 0 +THETA = 0 +ETA = 0 +KAPPA = 0.2) * *-------------------------------------------------------------------------- * .MODEL DGD D ( +IS = 1e-15 +RS = 0 +N = 1000 +TT = 0 +CJO = 1.129e-09 +VJ = 1.943 +M = 1.476 +EG = 1.11 +XTI = 3 +KF = 0 +AF = 1 +FC = 0.5 +BV = 10000 +IBV = 0.001) * *-------------------------------------------------------------------------- * .MODEL DBODY D ( +IS = 1.532e-11 +RS = 0 +N = 1.062 +TT = 2.5e-07 +CJO = 9.725e-10 +VJ = 1.127 +M = 0.6627 +EG = 1.11 +XTI = 5 +KF = 0 +AF = 1 +FC = 0.5 +BV = 671 +IBV = 0.00025) .ENDS .tran 1n 1u 0 1n .plot tran v(11,13) V(3,13) .probe .plot tran i(Xm1.ld) .end
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
25
Resistor Model Parameters (RDRAIN)
Model Parameter Description Unit Value Specified TC1 Linear temperature coefficient oC-1 0.008891 TC2 Quadratic temperature coefficient oC-1 3.056E-5
Resistor Model Parameter (RSOURCE)
Model Parameter Description Unit Value Specified TC1 Linear temperature coefficient oC-1 -0.003198 TC2 Quadratic temperature coefficient oC-1 2.60004E-5
Resistor Model Parameter (RDBODY)
Model Parameter Description Unit Value Specified TC1 Linear temperature coefficient oC-1 0.003945 TC2 Quadratic temperature coefficient oC-1 9.54752E-6
NMOS MOSFET Model Parameter
Model Parameter Description Unit Value Specified LEVEL Model index - 3 VTO Zero bias threshold voltage V 3.8 KP Transconductance coefficient amp/v2 13 GAMMA Bulk threshold parameter Volt1/2 2.6 PHI Surface potential V 0.6 RD Drain ohmic resistance Ohm 0 RS Source ohmic resistance Ohm 0 CBD Zero-bias bulk drain p-n capacitance Farad 0 CBS Zero-bias bulk source p-n capacitance Farad 0 IS Bulk p-n saturation current A 1E-14 PB Bulk p-n bottom potential V 0.8 CGS0 Gate-source overlap capacitance/channel width Farad/meter 0 CGD0 Gate-drain overlap capacitance/channel width Farad/meter 0 CGB0 Gate-drain overlap capacitance/channel length Farad/meter 0 RSH Drain, source diffusion sheet resistance Ohm/square 0 CJ Bulk p-n zero-bias bottom capacitance/area Farad/meter2 0 MJ Bulk p-n bottom grading coefficient - 0.5 CJSW Bulk p-n zero-bias sidewall capacitance/length Farad/meter 0
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
26
MJSW Bulk p-n sidewall grading coefficient - 0.33 JS Bulk p-n saturation current/area Amp/meter2 1E-14 TOX Oxide thickness Meter 1E-7 NSUB Substrate doping density 1/cm3 1E15 NSS Surface state density 1/cm2 0 NFS Fast surface state density 1/cm2 6.59E11 TPG Gate material type:
+1 = opposite of substrate -1 = same as substrate 0 = aluminium
- 1
XJ Metallurgical junction depth Meter 0 LD Lateral diffusion Meter 0 UO Surface mobility cm2/v-sec 600 VMAX Maximum drift velocity m/s 0 KF Flicker noise coefficient - 0 AF Flicker noise exponent - 1 FC Bulk p-n forward bias capacitance coefficient - 0.5 DELTA Width effect on threshold - 0 THETA Mobility modulation Volt-1 0 ETA Static feedback - 0 KAPPA Saturation field factor - 0.2
Diode Model Parameters (DGD)
Model Parameter Description Unit Value Specified IS Saturation current A 1E-15 RS Parasitic resistance Ohm 0 N Emission coefficient - 1000 TT Transit time Sec 0 CJO Zero-bias p-n capacitance Farad 1.129E-9 VJ p-n potential V 1.943 M p-n grading coefficient - 1.476 EG Bandgap voltage (barrier height) eV 1.11 XTI IS temperature exponent - 3 KF Flicker noise coefficient - 0 AF Flicker noise exponent - 1 FC Forward-bias depletion capacitance coefficient - 0.5 BV Reverse breakdown knee voltage V 10000 IBV Reverse breakdown knee current A 0.001
Electromagn
Diode Mod
Model Para IS RS N TT CJO VJ M EG XTI KF AF FC BV IBV
etic Interfere
del Paramete
ameter D SaPaEmTZep-p-BaISFlFlFoRR
nce (EMI) and
ers (DBODY
Description
aturation curarasitic resistmission coefransit time ero-bias p-n -n potential -n grading coandgap volta
S temperaturlicker noise clicker noise eorward-bias everse breakeverse break
Fig.
d filter design
Y)
rrent tance fficient
capacitance
oefficient age (barrier he exponentcoefficient exponent depletion ca
kdown knee vkdown knee c
18 – Step res
for SMPS
height)
apacitance covoltage current
sponse of Ga
oefficient
te-Source vol
Centre fo
U A
V
e
VA
ltage
or Airborne Sy
Unit Valu A 1.53Ohm 0 - 1.06Sec 2.5EFarad 9.72V 1.12- 0.66eV 1.11- 5 - 0 - 1 - 0.5 V 671 A 0.00
ystems, DRDO
ue Specified
32E-11
62 E-7 25E-10 27 627
0025
O
27
Electromagn
etic Interference (EMI) and
Fig.
F
d filter design
19 – Step res
Fig. 20 – Step
for SMPS
sponse of dra
p response of
ain-source vo
f drain curren
Centre fo
ltage
nt
or Airborne Syystems, DRDO
O
28
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
29
3. Measurement of EMI in DC-DC converters
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
30
WHAT ARE DC-DC POWER CONVERTERS
DC-DC power converters are employed in a variety of applications, including power supplies for personal computers, office equipment, aircraft power systems, laptop computers, and telecommunications equipment, as well as dc motor drives. The input to a dc-dc converter is an unregulated dc voltage Vg. The converter produces a regulated output voltage V, having a magnitude (and possibly polarity) that differs from Vg. For example, in the power supply system of the Airborne Early Warning & Control Systems (AEW&CS) the input supply of 200V/400Hz from the aircraft is rectified to 270V DC by a rectifier unit. This 270V DC is then supplied to a Multi-output power supply which converts this 270V DC into a number of smaller outputs using a DC-DC converter.
High efficiency is invariably required, since cooling of inefficient power converters is difficult and expensive. The ideal dc-dc converter exhibits 100% efficiency; in practice, efficiencies of 70% to 95% are typically obtained. This is achieved using switched-mode, or chopper, circuits whose elements dissipate negligible power. Pulse-width modulation (PWM) allows control and regulation of the total output voltage. This approach is also employed in applications involving alternating current, including high-efficiency dc-ac power converters (inverters and power amplifiers), ac-ac power converters, and some ac-dc power converters (low-harmonic rectifiers).
FLYBACK CONVERTER
Fly-back converter is the most commonly used SMPS circuit for low output power applications where the output voltage needs to be isolated from the input main supply. The output power of fly-back type SMPS circuits may vary from few watts to less than 100 watts. The overall circuit topology of this converter is considerably simpler than other SMPS circuits. Input to the circuit is generally unregulated dc voltage obtained by rectifying the utility ac voltage followed by a simple capacitor filter. The circuit can offer single or multiple isolated output voltages and can operate over wide range of input voltage variation. In respect of energy-efficiency, fly-back power supplies are inferior to many other SMPS circuits but it’s simple topology and low cost makes it popular in low output power range.
The commonly used fly-back converter requires a single controllable switch like, MOSFET and the usual switching frequency is in the range of 100 kHz. A two-switch topology exists that offers better energy efficiency and less voltage stress across the switches but costs more and the circuit complexity also increases slightly.
Electromagn
BASIC TOP
Fig. 21 showderived fromgenerally ofSince the SMspite of beinA fast switcthe desired between intransformerbe noted tsimultaneounormal tranampere turnSince primamore like transformerdone like threctificationAs can be sdiode and a
etic Interfere
POLOGY OF
ws the basicm the utility f low frequenMPS circuit ng unregulatching device,
output voltput and our are wound that the priusly and in nsformer, unns of primaryary and secotwo magnet
r as inductorhat for an in
n and filterinseen from tha capacitor. V
nce (EMI) and
FLYBACK C
c topology oac supply af
ncy and the is operated aed, may be clike a MOSF
tage. The trutput voltage
to have goodimary and sthis sense flnder load, py winding is
ondary windtically coupr-transformenductor. Th
ng, is considehe circuit (FigVoltage acros
Fig
d filter design
CONVERTER
f a fly-back fter rectificatoverall ripplat much highconsidered toFET, is used ansformer ise and currend coupling sosecondary wly-back trans
primary and nearly balanings of the fled inductorer. Accordine output secerably simplg.21), the secss this filter c
g.21 – Ideal f
for SMPS
R
circuit. Inpution and somle voltage waher frequenco have a cons
with fast dyns used for vnt requiremo that they a
windings of sformer worsecondary w
nced by the ofly-back tranrs and it m
ngly the magction of the ler than in mcondary win
capacitor is th
fly-back conv
ut to the cirme filtering. Taveform repecy (in the ranstant magnitunamic contrvoltage isola
ments. Primaare linked by
the fly-bacrks differentwindings co
opposing ampnsformer donmay be morgnetic circuit
fly-back tramost other swnding voltagehe SMPS out
verter schema
Centre fo
rcuit may beThe ripple ineats at twice nge of 100 kHude during aol over switction as well
ary and seconearly samek transformly from a nonduct simulpere-turns ofn’t conduct re appropriat design of ansformer, w
witched mode is rectified tput voltage.
atic
or Airborne Sy
e unregulatedn dc voltage the ac main
Hz) the inpuany high freqch duty ratiol as for bettondary winde magnetic flumer don’t ca
ormal transfltaneously suf the secondsimultaneou
ate to call ta fly-back trawhich consistde power sup
and filtered
ystems, DRDO
d dc voltagewaveform is
ns frequency.ut voltage, inquency cycle. to maintainer matching
dings of theux. It shouldarry currentformer. In auch that theary winding.
usly they arethe fly-backansformer ists of voltagepply circuits.
using just a
O
31
e s .
n .
n g e d t a e . e k s e . a
Electromagn
LINE IMPE
LISN is an converter insituation is
An LISN rea
1. It al2. It fe3. It p4. It p
rep
etic Interfere
DANCE STA
industrial encluding loadshown in Fig
alizes four im
llows supplyeeds and con
prevents exterpresents a croducibility
nce (EMI) and
Fig. 22 – Ou
ABILIZATION
element offed as an interfg. 23.
mportant task
ying the equipncentrates disrnal noise toonstant impfrom site to
d filter design
utput charac
N NETWOR
ered by stanface to make
ks
pment with Asturbance thr modify mea
pedance of 5site.
for SMPS
cteristics of an
K
ndards to ple it possible m
AC power (lorough the m
asurements 50Ω with re
n ideal fly-ba
lace betweenmeasuring th
ow frequencymeasurement
espect to fre
Centre fo
ack converter
n the supplyhe conducted
y behaviour)points.
equency whi
or Airborne Sy
y and powerd interference
) from the po
ich allows m
ystems, DRDO
r electronicse. The stated
ower mains.
measurement
O
32
s d
t
Electromagn
The adopted
etic Interfere
d LISN topol
nce (EMI) and
Fig. 2
logy is shown
Fig. 24 – Sc
d filter design
23 – Measure
n in Fig. 24.
hematic of L
for SMPS
ement setup f
ine Impedan
for conducted
nce Stabilizat
Centre fo
d EMI
ion Network
or Airborne Sy
ystems, DRDOO
33
Electromagn
It is evidentthus allowin
etic Interfere
Fig. 25 – Imp
Fig. 26 – Im
t from the Imng standardiz
nce (EMI) and
pedance offer
mpedance offe
mpedance cuzed measure
d filter design
red by LISN f
ered by LISN
urves that a Lment of EMI
for SMPS
for the full fr
in the high fr
LISN offers aI component
requency spec
frequency ran
a constant imt (10 kHz to
Centre fo
ctrum (10Hz
nge. (10 kHz t
mpedance of 30 MHz).
or Airborne Sy
to 100 MHz)
to 100 MHz)
50Ω at high
ystems, DRDO
)
)
frequencies,
O
34
,
Electromagn
MEASUREM
Fig. 27 –
The SPICE
REALIST .OPTION ******** INPUT Vinput Vgate 7 ******* * LISN Clisn1_Rlisn1_ Llisn1 Clisn1_Rlisn1_Rlisn1_ ******* * LISN Clisn2_Rlisn2_ Llisn2 Clisn2_
etic Interfere
MENT OF E
Circuit to me
net-list for th
TIC FLYBAC
N METHOD=G
**********T VOLTAGE
1 2 dc 307 8 pulse(
**********
1
_1 1 12 8u_1 12 0 5
1 3 50uH
_2 3 11 0._2 11 0 1k_3 11 0 50
**********
2
_1 2 10 8u_1 10 0 5
2 8 50uH
_2 8 9 0.2
nce (EMI) and
MI
easure EMI g
he above sho
CK CONVERTE
GEAR LVLTIM
**********
0V 0 10 0 10n
**********
u
25u k
**********
u
5u
d filter design
generated by
own schemat
ER
M=1
**********
n 10n 0.58
**********
**********
for SMPS
the fly-back
tic is as show
***********
8u 1u)
***********
***********
converter (w
wn below:
**********
**********
**********
Centre fo
ith parasitic
***********
***********
***********
or Airborne Sy
and realistic
******
******
******
ystems, DRDO
c elements)
O
35
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
36
Rlisn2_2 9 0 1k Rlisn2_3 9 0 50 ********************************************************************* * primary side of flyback converter R1 3 4 0.014 Cpar1 4 5 2.73nF Lpar1 5 6 1.58uH Xm1 6 7 8 mtp6n60/mc ********************************************************************* * flyback transformer LFPRIMARY 4 5 14u LFSECONDARY 0 13 0.6u KTX LFPRIMARY LFSECONDARY 0.99 ********************************************************************* * capacitor parasitics of flyback transformer CtxPar1 4 13 0.29nF CtxPar2 5 0 0.29nF ********************************************************************* * secondary side of transformer Cpar2 13 0 4.46nF Xd1 13 14 40EPS08 Cfilter 14 0 50uF Rload 14 0 3.2 ********************************************************************* * MOSFET subcircuit .subckt mtp6n60/mc 10 20 30 * * 10 = Drain 20 = Gate 30 = Source * ********************************************************************* * *------------------------ EXTERNAL PARASITICS ----------------------- * PACKAGE INDUCTANCE * LDRAIN 10 11 4.5e-09 LGATE 20 21 7.5e-09 LSOURCE 30 31 7.5e-09 * * RESISTANCES * RDRAIN1 4 11 RDRAIN 0.8036 RDRAIN2 4 5 RDRAIN 0.0084 RSOURCE 31 6 RSOURCE 0.02018 RDBODY 8 30 RDBODY 0.0135 * RGATE 21 2 5
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
37
* *-------------------------------------------------------------------- * *--------------- CAPACITANCES AND BODY DIODE ------------------------ * DBODY 8 11 DBODY DGD 3 11 DGD CGDMAX 2 3 2.7e-09 RGDMAX 2 3 1e+08 CGS 2 6 1.31e-09 * *-------------------------------------------------------------------- * *----------------------- CORE MOSFET -------------------------------- * M1 5 2 6 6 MAIN * *-------------------------------------------------------------------- * .MODEL RDRAIN R( +TC1 = 0.008891 +TC2 = 3.056e-05) * .MODEL RSOURCE R( +TC1 = -0.003198 +TC2 = 2.60004e-05) * .MODEL RDBODY R( +TC1 = 0.003945 +TC2 = 9.54752e-06) * * .MODEL MAIN NMOS ( +LEVEL = 3 +VTO = 3.8 +KP = 13 +GAMMA = 2.6 +PHI = 0.6 +RD = 0 +RS = 0 +CBD = 0 +CBS = 0 +IS = 1e-14 +PB = 0.8 +CGSO = 0 +CGDO = 0 +CGBO = 0 +RSH = 0 +CJ = 0 +MJ = 0.5 +CJSW = 0 +MJSW = 0.33 +JS = 1e-14 +TOX = 1e-07 +NSUB = 1e+15 +NSS = 0 +NFS = 6.59e+11 +TPG = 1 +XJ = 0 +LD = 0 +UO = 600 +VMAX = 0 +KF = 0 +AF = 1 +FC = 0.5 +DELTA = 0 +THETA = 0 +ETA = 0
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
38
+KAPPA = 0.2) * *-------------------------------------------------------------------- * .MODEL DGD D ( +IS = 1e-15 +RS = 0 +N = 1000 +TT = 0 +CJO = 1.129e-09 +VJ = 1.943 +M = 1.476 +EG = 1.11 +XTI = 3 +KF = 0 +AF = 1 +FC = 0.5 +BV = 10000 +IBV = 0.001) * *-------------------------------------------------------------------- * .MODEL DBODY D ( +IS = 1.532e-11 +RS = 0 +N = 1.062 +TT = 2.5e-07 +CJO = 9.725e-10 +VJ = 1.127 +M = 0.6627 +EG = 1.11 +XTI = 5 +KF = 0 +AF = 1 +FC = 0.5 +BV = 671 +IBV = 0.00025) .ENDS ********************************************************************* * diode subcircuit .SUBCKT 40EPS08 A K D1 A K 40EPS08 .MODEL 40EPS08 d ( +IS=1e-15 RS=0.00426912 N=0.926332 EG=0.6 +XTI=0.5 BV=800 IBV=0.0001 CJO=1e-11 +VJ=0.7 M=0.5 FC=0.5 TT=1e-09 +KF=0 AF=1 ) .ENDS ********************************************************************* .tran 1ms 10ms .plot tran V(10,0) .FOUR 10kHz 100 V(10,0) .probe .end
The results obtained from the simulation of the above circuit are shown below:
Electromagn
etic Interfere
Fig.2
nce (EMI) and
28 – Output v
d filter design
voltage of the
Fig. 29 –
for SMPS
e fly-back con
Output volta
nverter with p
age ripple
Centre fo
parasitic elem
or Airborne Sy
ments
ystems, DRDOO
39
Electromagn
etic Interference (EMI) and
Fi
d filter design
Fig. 30 – FF
ig. 31 – frequ
for SMPS
T of the outp
uency vs. live
put waveform
voltage (dBμ
Centre fo
m
V)
or Airborne Sy
ystems, DRDOO
40
Electromagn
etic Interference (EMI) and
Fig.
d filter design
32 – frequen
for SMPS
ncy vs. neutra
al voltage (dB
Centre fo
BμV)
or Airborne Sy
ystems, DRDOO
41
Electromagn
etic Interference (EMI) and
F
Fig
d filter design
ig. 33 – Com
g. 34 – Differ
for SMPS
mmon mode n
rential mode
noise (in dBμ
noise (in dBμ
Centre fo
V)
μV)
or Airborne Sy
ystems, DRDOO
42
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
43
4. EMI filter design for DC-DC converters
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
44
INTRODUCTION
The main purpose of the EMI filter is to limit the interference that is conducted or radiated from the power circuit. Excessive conducted or radiated interference can cause erratic behaviour in other systems that are in close proximity of, or that share an input source with, the power circuit. If this interference affects the power circuit, it can cause erratic operation, excessive ripple, or degraded regulation, which can lead to system level problems. Input EMI filters may also be used to limit inrush current, reduce conducted susceptibility, and suppress spikes. The specifications for the allowable interference are generally driven by the power circuit specification. The most common specifications include MIL-STD-461 for military applications and FCC for commercial applications. Many other EMI specifications also exist.
The basic requirements for an EMI filter are
The filter must provide the power converter with lower output impedance than the negative input resistance of the power circuit.
The input filter attenuation must be sufficient to limit the resulting interference to a level that is below the imposed specification.
This section deals with the design and analysis of EMI filters that will reduce conducted interference and conducted susceptibility.
TOPOLOGY OF AN EMI FILTER
The noise voltage, measured from the 50Ω LISN contains both common-mode (CM) noise and differential-mode (DM) noise. Each mode of noise is dealt with by the respective section of an EM1 filter. Fig. 33 shows a commonly used filter network topology, and Fig. 34 and 35 shows, respectively, the equivalent circuit of the CM section and the DM section of the filter. Referring to Fig. 34 and 35, it is noticed that some elements of the filter affect DM (or CM) noise only and some affect both DM and CM noise. The capacitors CX1 and CX2 affect DM noise only. An ideal common-mode choke LC affects CM noise only, but the leakage inductance Lleakage between the two windings of LC affects DM noise. CY suppresses both CM noise and DM noise, but its effect on DM noise suppression is practically very little because of the relatively large value of CX2. Similarly, LD suppresses both DM noise and CM noise, but its effect on CM noise is practically very little because of the relatively large value of Lc. The two modes of noise collectively contribute to the total EMI noise.
Electromagn
BASIS OF D
1. Comm
The commassumption
etic Interfere
DETERMINI
mon Mode
mon mode ens and theore
nce (EMI) and
Fig. 3
Fig. 37
NG FILTER C
quivalent cirems as show
d filter design
Fig. 35 – T
36 – Commo
7 – Differenti
COMPONEN
rcuit of Fig.wn in Fig. 36 –
for SMPS
Topology of a
n Mode nois
ial Mode noi
NT VALUES
. 34 is reduc– 39.
an EMI filter
e equivalent
ise equivalent
S
ced to an L
Centre fo
circuit
t circuit
C series circ
or Airborne Sy
cuit through
ystems, DRDO
h a series of
O
45
f
Electromagn
etic Interfere
Fig. 39
nce (EMI) and
Fig. 3
– Equivalent
Fig.40 –Equ
Fig. 41
d filter design
38 – Commo
t circuit of Fig
uivalent circu
1 – Filter atte
for SMPS
on mode noise
ig. 38 if ZP >>
uit of Fig. 39
enuation for c
If
w
App
CM
=
e equivalent
> ( ) and w
after recipro
common-mo
ZP >> ((LC + LD/2)
lying Recipro
M Attenuatio
, ∗, ∗ ≈
f
≈
Centre fo
circuit
w(Lc + Ld/2)
ocity theorem
de noise
) and
>> 25Ω
ocity theorem
on = ( (,,
fR,CM = √≈ .
or Airborne Sy
) >> 25Ω
m
m
) )
= ( If LC >> LD/
ystems, DRDO
)
/2
O
46
Electromagn
2. Differe
The differeassumption
etic Interfere
ential Mode
ential mode ns and theore
Fig. 43 – Eq
Fig
nce (EMI) and
equivalent cems as show
Fig
quivalent circ
g. 44 – Equiv
F
d filter design
circuit of Figwn in Fig. 40 –
g. 42 – Differe
cuit of Fig. 42
valent circuit
Fig. 45 – Filte
for SMPS
g. 35 is redu– 43.
ential Mode e
2 if ZCX1 >> 1
of Fig. 43 by
er attenuatio
Re
If C
uced to an L
equivalent ci
100Ω; ZCX2 >
applying rec
n for DM no
If >>
wLDM >> 10
ciprocity the
CX1 = CX2 = CD
f
=
Centre fo
LC series cir
rcuit
>> ZP; and wL
ciprocity theo
ise
100Ω,
00Ω
eorem
DM
fR,DM = √= (
or Airborne Sy
rcuit through
LDM >> 100Ω
orem
>> ZP
)
ystems, DRDO
h a series of
Ω
O
47
f
Electromagn
SOFTWAR
Fig. 44 shofollowing e
VL = VCM +
VN = VCM -
Therefore,
VDM = (VL
Fig. 46 –
etic Interfere
E BASED EM
ows the circequations can
+ VDM
- VDM
VCM = (VL +
– VN) / 2
Circuit diag
nce (EMI) and
MI NOISE SE
uit diagram n be derived.
+ VN) / 2, and
gram for sepa
signals
d filter design
EPARATION
for separati.
d
aration of con
for SMPS
N METHOD
ion of condu
nductive EMI
uctive EMI s
I
Fig.sep
C
Centre fo
signals. As s
47 – Flow charation of co
Measu
Measur
Conversion
Calculation oabove def
Conversion
or Airborne Sy
shown in th
hart of softwaonductive EM
Start
urement of V
rement of VN
n of VL & VN
of VCM & VDM
fined equatio
n of VCM & VdBμV
End
ystems, DRDO
e figure, the
are based MI signals
VL
N
in μV
M by the ons
VDM in
O
48
e
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
49
DESIGN PROCEDURE FOR EMI FILTER
Step 1: Accurately measure the base-line of common mode EMI noise spectrum VCM and differential mode EMI noise spectrum VDM.
Step 2: Determine the required common mode noise attenuation & differential mode noise attenuation at various sampled frequencies.
(Vreq-cm)dB = (VCM)dB – (Vlim)dB + 6dB
(Vreq-dm)dB = (VDM)dB – (Vlim)dB + 6dB
To avoid design error, +6dB is added because both the measured DM noise and CM noise are 3dB above the actual values, and because the measured CM & DM noise voltages may be in phase, which will cause a total error of 6dB in estimating the required attenuation.
Step 3: Determine filter corner frequencies The filter corner frequencies can be determined by searching the minimum values of fc-cm and fc-dm from the required attenuation from all sampled frequencies.
(Vreqd-CM))dB = 40log fc-cm = common mode corner frequency
(Vreqd-DM))dB = 40log fc-dm = differential mode corner frequency
Step 4: Determine filter component values a. CM components LC and CY:
Since there is a safety leakage current requirement, CY is normally limited to 3300pF. LC and 2CY should have a resonant frequency of fC-CM obtained in Step 3. Therefore
LC = ( ) ×
b. DM components LD, CX1 and CX2:
Based on the assumption made for Fig. 43, CX1 and CX2 are selected to be the same value CDM and are related to LDM through corner frequency fc-dm requirement as shown below
CX1 = CX2 = CDM = ( ) ×
CX1, CX2, LD are unknowns. There exists a degree of freedom for trade-off. Since the leakage inductance due to the coupling imperfection of a practical CM choke also has a filtering effect on the DM noise, thus to reduce the EMI filter design cost and size, the effect of the DM inductance LD can be totally replaced by the leakage inductance Lleakage of the CM choke. Practically, Lleakage is generally in the range of 0.5-2% of the Lc value.
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
50
Fig. 48 – Design steps of the presented filter design
Start
Separated CM and DM components
Limit line
Calculate the required CM and DM attenuation
Compute the CM and DM corner frequencies
Calculate the CM inductor value given that the Y-capacitor is fixed at 3300pF
Calculate the leakage inductance of the CM inductor
Calculate the value of CX1= CX2=CDM.
End
Electromagn
SOFTWAR
A MATLAdeterminati
Some of the
1. Req2. Allo3. Allo
For an expeconverter [SEMI filter isvoltage to 4has been ext
The results
etic Interfere
E IMPLEME
AB GUI wasion of EMI fi
e features of t
quires live voows pre-selecows design oa. FCC Clb. FCC Clc. MIL ST
Fi
erimental verSee Page – 4s chosen to c
45dBμV for atended over
obtained fro
nce (EMI) and
ENTATION O
s developed ilter compon
the GUI are
oltage and thecting the Y-C
of EMI filter alass A lass B, and
TD
ig. 49 –Devel
rification of t41] is used. Tcomply with a frequency rthe full cond
om the GUI a
d filter design
OF EMI FILT
using the nent values.
e neutral lineCapacitor valaccording to
loped MATL
the developeThe live volta
FCC Class Arange of 450 ducted EMI s
are shown be
for SMPS
TER DESIGN
above descr
e voltage as ilue and the l
o 3 standards
LAB GUI for
ed GUI, the dage and the A standard. F kHz to 30Mspectrum i.e.
elow.
ribed metho
inputs to comeakage induc
conducted EM
data obtainedneutral volta
FCC Class AMHz, but for
. 10 kHz to 3
Centre fo
ods and algo
mpute the filtctance of the
MI filter desig
d from the siage are loade
A standard limthis simulati0MHz.
or Airborne Sy
orithms to
ter componee CM inducto
ign
imulation ofed into the Gmits the condtion, the freq
ystems, DRDO
help in the
ent values. or.
f the fly-backGUI and theducted noise
quency range
O
51
e
k e e e
Electromagn
The values f
Common M
C
Differentia
C
etic Interfere
for the EMI f
Mode filter
CY = 3300 nF
al Mode filter
CX = 10.223 μF
nce (EMI) and
Fig. 50 – EM
filter as sugg
F
r
F
d filter design
MI filter resu
gested by the
for SMPS
lts obtained f
GUI are
LC = 0.2949
LD =2.949 m
for the fly-ba
H
mH
Centre fo
ack converter
Corne
Corne
or Airborne Sy
er freq. = 0.1
er freq. = 0.9
ystems, DRDO
1408 kHz
1662 kHz
O
52
Electromagn
SPICE VERI
With the daand it was in
It can be see
etic Interfere
IFICATION O
ata obtainedntegrated wi
en that the fi
nce (EMI) and
OF THE DES
d from the Gith the fly-ba
Fig. 51 –
Fig. 52 –
ilter effective
d filter design
SIGNED EM
GUI, an EMIck converter
– EMI filter u
– Attenuation
ly attenuates
for SMPS
I FILTER
I filter was dr earlier desig
using the data
n curve for th
s signals with
designed. Its gned, and the
a obtained by
he EMI filter
h frequency o
Centre fo
attenuation e EMI charac
y the GUI
designed.
over 10kHz i
or Airborne Sy
properties wcteristics wer
i.e. EMI nois
ystems, DRDO
were derivedre studied.
e.
O
53
d
Electromagn
To study thand neutral
The SPICE
LISN FO .OPTION ******** INPUT Vinput Vgate 7 ******* * LISN Clisn1_Rlisn1_ Llisn1 Clisn1_Rlisn1_Rlisn1_ ******* * LISN Clisn2_Rlisn2_ Llisn2 Clisn2_Rlisn2_
etic Interfere
e effectiveneline voltages
net list for th
OLLOWED BY
N METHOD=G
**********T VOLTAGE
1 2 dc 307 18 pulse
**********
1
_1 1 12 8u_1 12 0 5
1 3 50uH
_2 3 11 0._2 11 0 1k_3 11 0 50
**********
2
_1 2 10 8u_1 10 0 5
2 8 50uH
_2 8 9 0.2_2 9 0 1k
nce (EMI) and
ess of the EMs are again co
Fig. 53 – LI
he above sho
Y EMI FILTE
GEAR LVLTIM
**********
0V e(0 10 0 10
**********
u
25u k
**********
u
5u
d filter design
MI filter desigollected and
ISN followed
wn schemati
ER AND FLY
M=1
**********
0n 10n 0.5
**********
**********
for SMPS
gned, it is intestudied.
d by EMI filte
ic is as follow
YBACK CONVE
***********
58u 1u)
***********
***********
egrated with
er and fly-bac
ws:
ERTER
**********
**********
**********
Centre fo
the fly-back
ck converter
***********
***********
***********
or Airborne Sy
k converter an
******
******
******
ystems, DRDO
nd the live
O
54
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
55
Rlisn2_3 9 0 50 ********************************************************************* * EMI filter CX1 3 8 10.223u LC1 3 15 0.2949H LC2 8 16 0.2949H KEMI LC1 LC2 0.99 LD1 15 17 2.949mH LD2 16 18 2.949mH CX2 17 18 10.223u CY1 17 0 3300n CY2 18 0 3300n ********************************************************************* * primary side of flyback converter R1 17 4 0.014 Cpar1 4 5 2.73nF Lpar1 5 6 1.58uH Xm1 6 7 18 mtp6n60/mc ********************************************************************* * flyback transformer LFPRIMARY 4 5 14u LFSECONDARY 0 13 0.08u KTX LFPRIMARY LFSECONDARY 0.99 ********************************************************************* * capacitor parasitics of flyback transformer CtxPar1 4 13 0.29nF CtxPar2 5 0 0.29nF ********************************************************************* * secondary side of transformer Cpar2 13 0 4.46nF Xd1 13 14 40EPS08 Cfilter 14 0 50uF Rload 14 0 3.2 ********************************************************************* * MOSFET subcircuit .subckt mtp6n60/mc 10 20 30 * * 10 = Drain 20 = Gate 30 = Source
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
56
* ********************************************************************* * *------------------------ EXTERNAL PARASITICS ----------------------- * PACKAGE INDUCTANCE * LDRAIN 10 11 4.5e-09 LGATE 20 21 7.5e-09 LSOURCE 30 31 7.5e-09 * * RESISTANCES * RDRAIN1 4 11 RDRAIN 0.8036 RDRAIN2 4 5 RDRAIN 0.0084 RSOURCE 31 6 RSOURCE 0.02018 RDBODY 8 30 RDBODY 0.0135 * RGATE 21 2 5 * *-------------------------------------------------------------------- * *--------------- CAPACITANCES AND BODY DIODE ------------------------ * DBODY 8 11 DBODY DGD 3 11 DGD CGDMAX 2 3 2.7e-09 RGDMAX 2 3 1e+08 CGS 2 6 1.31e-09 * *-------------------------------------------------------------------- * *----------------------- CORE MOSFET -------------------------------- * M1 5 2 6 6 MAIN * *-------------------------------------------------------------------- * .MODEL RDRAIN R( +TC1 = 0.008891 +TC2 = 3.056e-05) * .MODEL RSOURCE R( +TC1 = -0.003198 +TC2 = 2.60004e-05) * .MODEL RDBODY R( +TC1 = 0.003945 +TC2 = 9.54752e-06) * * .MODEL MAIN NMOS ( +LEVEL = 3 +VTO = 3.8 +KP = 13 +GAMMA = 2.6 +PHI = 0.6 +RD = 0 +RS = 0 +CBD = 0 +CBS = 0 +IS = 1e-14 +PB = 0.8 +CGSO = 0 +CGDO = 0 +CGBO = 0 +RSH = 0 +CJ = 0 +MJ = 0.5
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
57
+CJSW = 0 +MJSW = 0.33 +JS = 1e-14 +TOX = 1e-07 +NSUB = 1e+15 +NSS = 0 +NFS = 6.59e+11 +TPG = 1 +XJ = 0 +LD = 0 +UO = 600 +VMAX = 0 +KF = 0 +AF = 1 +FC = 0.5 +DELTA = 0 +THETA = 0 +ETA = 0 +KAPPA = 0.2) * *-------------------------------------------------------------------- * .MODEL DGD D ( +IS = 1e-15 +RS = 0 +N = 1000 +TT = 0 +CJO = 1.129e-09 +VJ = 1.943 +M = 1.476 +EG = 1.11 +XTI = 3 +KF = 0 +AF = 1 +FC = 0.5 +BV = 10000 +IBV = 0.001) * *-------------------------------------------------------------------- * .MODEL DBODY D ( +IS = 1.532e-11 +RS = 0 +N = 1.062 +TT = 2.5e-07 +CJO = 9.725e-10 +VJ = 1.127 +M = 0.6627 +EG = 1.11 +XTI = 5 +KF = 0 +AF = 1 +FC = 0.5 +BV = 671 +IBV = 0.00025) .ENDS ********************************************************************* * diode subcircuit .SUBCKT 40EPS08 A K D1 A K 40EPS08 .MODEL 40EPS08 d ( +IS=1e-15 RS=0.00426912 N=0.926332 EG=0.6 +XTI=0.5 BV=800 IBV=0.0001 CJO=1e-11 +VJ=0.7 M=0.5 FC=0.5 TT=1e-09 +KF=0 AF=1 )
Electromagn
.ENDS ******* .TRAN 1.probe .end
The results
etic Interfere
**********
10E-004 0.
obtained fro
Fig. 54
nce (EMI) and
**********
01 7E-3
om the simul
4 – Output v
d filter design
**********
ation of the a
voltage of the f
for SMPS
***********
above circuit
fly-back con
**********
t are shown b
verter with L
Centre fo
***********
below:
LISN and EM
or Airborne Sy
******
MI filter
ystems, DRDOO
58
Electromagn
etic Interference (EMI) and
Fig.
Fig. 56
d filter design
55 – Output
6 – FFT of th
for SMPS
t voltage ripp
he output volt
ple with EMI f
tage with EM
Centre fo
filter
MI filter
or Airborne Sy
ystems, DRDOO
59
Electromagn
etic Interference (EMI) and
Fig. 57 – f
Fig. 58 – fre
d filter design
frequency vs.
equency vs. n
for SMPS
live voltage
neutral voltag
with EMI filt
ge with EMI f
Centre fo
ter (dBμV)
filter (dBμV)
or Airborne Sy
ystems, DRDOO
60
Electromagn
etic Interference (EMI) and
Fig. 59 –
Fig. 60 –
d filter design
– Common m
Differential
for SMPS
mode noise w
mode noise w
ith EMI filter
with EMI filte
Centre fo
r (dBμV)
er (dBμV)
or Airborne Sy
ystems, DRDOO
61
Electromagn
COMPARIS
On comparimprovemeintegration
Fig. 61 (A)
Fig. 62 (A
etic Interfere
SON OF RES
ring the comnt can be seeof the EMI f
Withou
– common m
A) – different
nce (EMI) and
SULTS OBTA
mon and difen. The commfilter thus, va
ut EMI filter
mode noise w
tial mode noifilter
d filter design
AINED WITH
fferential momon and dif
alidating the f
r
without EMI f
se without EM
for SMPS
H AND WIT
ode noise levfferential mofilter as effec
filter F
MI Fig
THOUT FILTE
vels with andode noises shctive.
Fig. 61(B) – co
g. 62 (B) – diff
Centre fo
ER
d without theow a signific
With EMI
ommon mode
fferential mo
or Airborne Sy
e EMI filter, cant attenuat
I filter
e noise with E
de noise with
ystems, DRDO
a significanttion after the
EMI filter
h EMI filter
O
62
t e
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
63
5. CONCLUSION
The switching characteristics of a Power MOSFET and the reverse recovery characteristics of a diode are the main contributors to EMI generated in a power converter. Both the characteristics were successfully modelled, tested and integrated in the converter and the EMI data was generated. An EMI filter was developed using the data generated by the converter. This filter was then integrated into the converter schematic and the EMI characteristics were simulated. A significant improvement in the EMI attenuation was observed.
In chapter 1, a basic overview of EMI/EMC was provided. The foundation stone for further EMI studies was laid down in the chapter. The reasons for occurrence of EMI and the modes of occurrence were discussed.
In chapter 2, high frequency models of components used in power converters were modelled. These included basic components such as the capacitor and inductor and switching components like the MOSFET. SPICE models for a diode and a MOSFET were developed to be used in the EMI simulation of a power converter.
In chapter 3, the basic concepts of a fly-back converter were discussed. Also the high frequency models of MOSFET and diodes were integrated into the converter and the circuit was simulated to determine the EMI characteristics of the converter.
In chapter 4, the data generated from the simulation in chapter 3 was used to design an EMI filter. A MATLAB GUI was developed for the purpose. The attenuation properties of the designed filter were studied and it was integrated in the fly-back converter. Thus a complete fly-back converter was simulated and the EMI data was again generated. The data so obtained (after the filter was integrated) was compared to the data previously obtained for the same converter and a significant improvement in the EMI characteristics was observed.
On the whole, a model for EMI simulation in a fly-back converter was developed bottom up. A complete SPICE program for the same has also been provided that can be used in further studies.
Electromagnetic Interference (EMI) and filter design for SMPS Centre for Airborne Systems, DRDO
64
6. REFERENCES
[1] Dong-Young Lee, J.H. Lee, S.H. Min, B.H. Cho, B.H. Lee. “Exact Simulation of Conducted EMI in Switched Mode Power Supplies”, SAE ’98.
[2] Fu-Yuan Shih, Dan Y. Chen, Yan-Pei Wu, Yei-Ton Chen. “A Procedure for Designing EMI Filters for AC Line Applications”, IEEE transactions on Power Electronics, Vol. 11, No. 1, January ’96.
[3] Po-Shen Chen, Yen-Shin Lai. “New EMI Filter Design Method for Single Phase Power Converter using Software-based Noise Separation Method”, IEEE ’07.
[4] Himanshu K. Patel. “Critical Considerations for EMI Filter Design in Switch Mode Power Supply”. [5] Jukka-Pekka SjÖroos. “Conducted EMI filter design for SMPS”, IEEE ’06. [6] Hsin-Lung Su, Ken-Huang Lin. “Computer-Aided Design of Power Line Filters with a Low Cost
Common- and Differential-Mode Noise Diagnostic Circuit”, IEEE ’01. [7] A. Farhadi, A. Jalilian. “Modelling and Simulation of Electromagnetic Conduced Emission Due to
Power Electronics Converters”, IEEE ’06. [8] Thomas Farkas. “A Scientific Approach to EMI Reduction in Switching Power Supplies”, MS Thesis,
Massachusetts Institute of Technology, September ’91. [9] MIL-STD-462. Military Standard: Measurement of Electromagnetic Interference Characteristics.
[10] Andreas Karvonen. “MOSFET Modelling Aimed at Minimizing EMI in Switched DC/DC Converters Using Active Gate Control”, Engineering Thesis, Chalmers University of Technology, 2009.
[11] Liyu Yang. “Modelling and Characterization of a PFC Converter in the Medium and High Frequency Ranges for Predicting the Conducted EMI”, MS Thesis, Virginia Polytechnic Institute and State University, September ’03.
[12] C.H. Xu, D. Schroder. “Modelling and Simulation of Power MOSFET’S and Power Diodes”, IEEE PESC ’88.
[13] Gabriel Chindris, Ovidiu Pop, Grama Elin, Florin Hurgui. “New PSpice model for Power MOSFET devices”, IEEE International Spring Seminar on Electronics Technology, May ’01.
[14] Hong Man Leung. “SPICE Simulation and Modelling of DC-DC Flyback Converter”, MS Thesis, Massachusetts Institute of Technology, August ’95.
[15] Peter O. Lauritzen. “A Simple Diode Model with Reverse Recovery”, IEEE transaction on Power Electronics, Vol. 6, No.2, April ’91.
[16] C. Chang, H. Teng, J. Chen, H. Chiu. “Computerized conducted EMI filter design system using labVIEW and its applications”.
[17] Mohit Kumar, Vivek Agarwal. “Power Line Filter Design for Conducted Electromagnetic Interference Using Time-Domain Measurements”, IEEE transaction on Electromagnetic Compatibility, Vol. 48, No. 1, February ’06.
[18] Mohannad Lutfi Nayfah, Ali Keyvan Ekbatani, Abdullah Albisher. “Power Line Filter Design for Conducted Electromagnetic Interference Using Time-Domain Measurements”,
[19] Supratim Basu. “EMI-EMC Notes”. [20] “Fly-Back Type Switched Mode Power Supply”, Module-3, Lecture-22, Power Electronics, IIT
Kharagpur, NPTEL. [21] MicroSim Application Notes, MicroSim. [22] Reference Manual, OrCAD PSpice A/D, OrCAD Inc.