art ieee 01- e.f. magnus - tool for conducted em1 and filter design - emi_01

7/28/2019 Art IEEE 01- E.F. Magnus - Tool for Conducted EM1 and Filter Design - EMI_01

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Tool for Conducted EM1 and Filter Design

Elio Frei tas Magnus, J ~ l i o . M. de Lima, V. M. Canalli, J. A. Pomilio and F. S . Dos Rei.s

Pontificia Universidade Catblica do Rio G rande do SUIFaculdade de Engenharia

Departamento de Engenha ria EletricaAvenida Ipiranga, 6681 - Porta Alegre -RS

CEP 90619-900 - Brasile-mail: [email protected]

Abstract - In this paper a s imulat ion tool that al lows us t o

deter min e the conducted Electromagnetic Interference

(EMI), genera ted fo r the bas ic PFP conver ter s (Cuk ,Buck, Boost, Buck-Boost, Sepic, an d Zeta co nve rters) will

be presented. Using this Sof tware, we can determ ine full

EM 1 spectrum in dB/vV in accordance with the CISPR16 s tandard . An EM 1 filter design m ethodology tha t allow

us t o accommodate the conducted ElectromagneticInterference (EMI) generated by power factor correctorsto international s tandards in the design step is alsopresented. Therefore, this can be an useful aid for pow erelectronics designers.Keywords EM I, PFPs, Filter.

(first harmonic) in dElipV in accordance with the

International Special Committee on Radio Interferencepublication 16 (CISPR 16) [3] standard, for (Cuk, Buck,Boost, Buck-Boost, Sepic and Zeta) converters workmg as

PFP, in all operates modes Continuous Conduction Mode(CCM), Discontinuous Conduction Mode (DCM) and

Frequency Modulation (FIM) as proposed by Alhach [4]. Inthat work the authors only present the first harmonic [4]. Th ecurves are made taking into account a simulation of themeasuring apparatus io accordance with CISPR 16. A very

good method for this simulation was presented by Albach

~41.

I. INTRODUCTION

A crucial task in the recent years has been the reduction ofthe product development time, because the product lifetimehas become shorter quickly. Keeping this in mind, isimportant to minimize the EM1 failures in the design time,because the real cost of EM1 compliance failing is not thecharge made to EMC credential laboratories for testing andre-testing, that can be expensive, with Test House fees up toU$ 1,500.00 per day. These fees fade into insignificance

when compared with the impact of the resulting delay onproduct time to market [I].

The influence of the EM1 injected into the AC line by thepower converters working as Power Factor Preregulators

(FFP) in the electronic design is becoming more and moreimportant. This is because the converters need to fulfil theintemational standards for EM1 of current and future

regulation limits of conducted and radiated noise generation.

These regulations also limit the minimum power factor forthe equ ipment connected to the AC'Iine.All these facts demonstrate the importance of the EM1

analysis of power converters working as Power FactorPreregulator (PFP).

A method for determination of PFP conductedElectromagnetic Interference (EMI) emission was presentedby Dos Reis et al [2]. Which it was based, in a group ofcurves as you can see in figure 1, that allow us to determinethe amplitude of the conducted EM1 Differential Mode (DM)

Fw-w (M-1

Fig. 1: Example of EM1 design curves

In this work a full simulation tool is presented. This toolwas developed in order to run in a Personal Computer andcan simulate the entire EM1 spectrum. Using this Software itis possible to determinate with very good accuracy theconducted EM1 before build a prototype. This informationcan contribute to reduce the product development time andtherefore the cost.

This software permit the sim ulation of the Line ImpedanceStabilization Network (LISN) like you can see in figure 2

and the EM1 receiver parts; (input filter, demodulator, Quase-Peak Detector and Mechanical Measurement Apparatus) likeyou can see in figure 3, in accordance with the CISPR 16standard. Using the proposed software tool, the EM1 curvescan be obtained from sirnulation analysis. The CISPR 16

0-7803-7906-3/03/$17.00 0 20 03 IEEE. 2326

Ref x EMI

mailto:[email protected]

mailto:[email protected]



establish a standardized way to determinate the EM1spectrum. In order to comply with CISPR 16 standards, anEM1 receiver must include a filter with specifiqd bandwidthsand shapes, an envelope detector, a quasi-peak detector and ameter with time constanls specified like in table 1. In thefollow sections an example of the mathematical harmonic

analysis obtained for Sepic and Cuk converters is presented.

BANDWIDTH

Discharge time constant (dMechanical time constant ( T d

Chargetimeconstan1 (TI)

+20 %Maximum Tolcrance I

~~~~.. . ~

150kHz 3 0 M H z ' ' MH z

220Hz 9% I 2 0 k H z

4 5 M 1M I M500 ms 160ms 550m

I60 ms 160ms 100mS

40 -

1 1 0O T , 1 1 1 , , . ,

0.01 0.1

Fig. 2. Line Impedance Stabilization Network.

- I I(C)

Fig. 3. EM1 receiver parts (a) input filter, (b) demodulator,(c) quasi-peak detector and m echanical meas. apparatus.

TABLE IMEASUREMENTSpLClFlCATlONSACCORDD?GTOClSPR 16

Range of Crcquencv

Charactcisties 101" I O l J f " I 3 0 1 0 1 0 0 0

11. HARMONIC ANALYSIS OF THE INPUT CURRENTFOR SEPIC AND CUK

The EM1 simulation is obtained from the input currentharmonic analysis of the studied converter and from thesimulation of the LISN and EM1 receiver. .T h e highfrequency current harmonics flows through the LISN whichis a current voltage transducer (fig. 2) the voltage at theoutput of the LISN is applied to the EM 1 input filter receiverfig. 3 (a), after that the interference v oltage U,.,(t) is appliedto the envelope detector fig. 3 (b), the demodulated voltageUD t) is applied to tbe quasi-peak detector and finally the

result is shown in the meter fig. 3 (c). In this section wepresent the harmonic analysis of the input inductor current iLI

for Sepic and Cuk converters as PFP in DiscontinuousConduction Mode (DCM). The same analysis can beextended to the others basic PFP converters working in alloperation modes.

The basic structures of the Sepic and Cuk converters areshown in Fig. 4. In order the results obtained for the Boostconverter are showed in this paper, thereunto, the buckconverter results are showed too.

For the present analysis, the elements in Fig. 4 will beconsidered as follows:

a) Inductors L , and L2 will be represented by its inductance.b) The output capacitor Cr is represented as a voltage source,because C fis large enough.c) A11 semiconductors are ideal switches.d) The voltage v, denotes the rectified mains input voltage

vg =V, I sin wt 1 where V, is the pea k value of the mainsinput voltage (vc), w =2nf and f is the line voltage frequency.In a S.F . period we co nsider v, con stant and its value is v, =

Vgl sin w t l i 1 We can make this simplification because theline voltage has a frequency (50 - 60 H z) which is muchlower than the S.F.

e) The capacitor C , voltage follows the input voltage in a lineperiod as described by Simonetti et a1 [ 5 ] .

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+Yc

(h )

Fig. 4. Sepic and Cuk c onverters (a) and (b) respectively.

The Sepic and Cuk converters in DC M presen t an averageinput current proportional to the inp ut voltage in a switchingperiod as shown in [ 6 ] . t can be dem onstrated that, Sepic and

Cuk con verters when opera ting as PFP in DC M have thesame input current. Therefore, the analysis made for Sepicconverter is also valid for Cuk converter. Throughout thispaper, the results obtained for Sepic converter is the same as

the results obtained for Cuk conv erter.

The input current for Sepic and Cuk converters as PFP inDCM, within a S.F. period, is given as a function of the timeinstants tli, t2i, tli an d hi. The index i = 1, 2 ... I, represent the

numbers of the S.F. periods within one half-wave period ofthe input voltage vg. The 1 value is defined as I =fs I ( 2 . 0 f),

in the case of constant switching frequency. In Fig. 5 we

show the input current as a function of the time instants t l i ,

tZi, t an d hi, for one switch period of a Sepic or Cuk

converter as PFP in DCM. In the Table 11, the time intervals

are best explaine d.

TABLE I1

TIME TERVALS.

1,i m i s t o r becomes conducting.

IIx transistor becomes non-conducting.

4.mis t o rbecomes conducting again.

To kn ow the cond ucted EM1 DM generated by thesecon verte rs, we nee d to Imow the high frequency Fouriercoefficie nts. The Fouri er ,:xpansion of the input curre nt canbe expressed by equation ( I ) .

The coefficientsa. nd b. :have been c alcu lated as in [4],

where:

n

wr=- ...... w = 2@ (4)

""....... .... ..... ,

~ ~ .................. T ~ ~~:

Fig. 5. Input current as a function of time intervals.

Ill. EM1 TOOL DESCRIPTION

In this section will be presented a description of the

sofhvare that allows to determine the conducted EM1 in

dB/pV for the more em ployed PFP conv erters, in accordanc e

to the CISPR 16 [3] standard. This tool can be used fordevelopment of the Boost, Buck, Buck-Boost, Zeta, Sepican d Cuk converters.

The m ain parts of the sofhvare are described in the followsteps:

*Th e calculation of input current for the cited convertersin high frequency (h.f.). An example of input data isshown in the figure 6.*To obtain the Fourier coefficients a.and b, of the inputcurrent. This coe fficients for all converters can be

obtained as for Sepic and Cuk converters. To check theobtained coefficients the tool supply an input currenttime doma in as shown in figure 7.

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aT o obtain the interference voltage, simulating the input

.To simulate measurements apparatus in accordance to

.To show in graphic forms the conducted EM I. An

current across of the artificial mains network (LISN).

ClSPR 16, using the characteristics of the table 1.

example is showed in figure 8.

It is important to observe that at f, = 150 l cHz the curveshave a discontinuity. This discontinuity at 150 kHz has itsorigin in the CISPR 16 , which establishes changes in themeasurement apparatus at this frequency. The mostimportant change occurs in the bandwidth of the receiver thatchanges from 200 Hz to 9 Wz.

For validation of this tool, results obtained in [4] and [7]were compared and showed that for few steps of calculation,they are very good.

. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . ., . , I .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . .

. . . . . . . . . .. . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . .. , . , . , . .. . . . . . . . . . .

Fig. 7: Simulated input current for boost converter.

23

iq1 ,?e" , ; ; E n ' . r F w , . .a'., - - V i ) F " 3 7 ! . C 1 . . l i I._. . . . - . .............. _.- .

d

F ig. 8 : Graphical output for Conducted EM I .

1V. EM1 FILTER DESIGN CONSIDERATION S

The design of a suitable EM1 filter can be d one accordingdifferent approaches [7-91. Usually a high-order filter is used

to reduce inductance and capacitance values.Ideally it could be considered that no harmonic

components exist in the frequency range between the line andthe switching frequencies. This fact would allow to center thefilter resonance at a suitable frequency in order to guaranteethe required attenuation. In this ideal situation the filter couldbe undamped.

In the Continuous. Conduction Mode the input rectifiedvoltage is usually used to create the current referencewaveform. In this case the presence of instabilities in thefilter output (converter side) can lead to severe conveitermalfunction [IO].

As the input voltage waveform is not so important for theproper operation of the PFC in the Discontinuous Conduction

Mode, some damping effect is necessary to avoid oscillationsin the average input current produced by transient situations,like load or line changes.

According to the paper proposition, the filter will bedesigned considering only the differential mode EM1 noise

produced by the converter. For this type of filter, not only therequired attenuation but also other restrictions must be takeninto account. For example, VDE standard specifies a

maximum x-type capacitance of 2.2 pF [8] in.order to limitthe line current ( 50160 Hz component) even at no loadsituation. The maximum capacitance should be used to

minimise the inductance value.Let us consider the damped second order filter topology

shown in figure 9. This filter attenuates 40 dBidec. For a

given necessary attenuation, the cut-off frequency is givenby:

(1),f, =

10%

where f, is the cut-off frequency, f, is the frequency in whichthe required attenuation (A,) is determined. A2 is the filtercharacteristic attenuation.

29



The inductance value is given by:

1L,'=

47t2C1f,2

The maximum CI+C2 alue is 2.2 pF [SI, and for a properdamping effect, C2 =IOC I. The d amping resistance can be

calculated as:

R,: -J: (3)

Converter sideine side -0

0I A- 0

Fig. 9 EM1 differential mode filter.

V . FILTER DESIGN EXAMPLE

The standard IEC CISPR 11 [ l I] determines limits forconducted noise for industrial, scientific and medicalequipment (ISM). The limit for mains terminal disturbance

voltage in the frequency band 15 0 ldIz to 50 0 ldIz is 66dBip V (average level), measured according to CISPR 16 .

Le t us consider a boost PFC, in DCM, and the 102 dB/pVpredicted EM1 level shown in Fig. 8. The required filterattenuation is 36 dBIpV. To have this value at 150 kHz, asecnnd-order filter must have a cut-off frequency at 18.9kHz

(equation (38)). Adopting C 1=220 nF a nd C2 =2 pF, the

inductance (equation (39)) and damping resistance (equation(40)) are, respectively, 322 pH an d 38 n. Figure 10 showsthe filter frequency response, given the 36 dB attenuation at

15 0 kHz.

VI. EXPERIMENTAL RESULTS

For experimental validation of the proposed tool, a Boost,a Buck, a Sepic and a Zeta converters prototypes wereimplemented and tested at Labelo (a credential measurem entlaboratmy). Underwriters Laboratories Inc. of the USA

recognize this Laboratory The experimental EM1 result forthe Boost converter are shown in Fig. 11 .

The results obtained by ?:he proposed EM1 tool for Boostconverter are shown in Fig. 8. The simulations and theimplemented prototype for Boost converter was made using

the specifications shown in the input panels o f the Fig. 6. Th eresults obtained in the lab were compared with the results ofthe simulation and are presented in the Table 111.

Fig. 11 . Experimental results for the Boost C onverter test.

TABLE 111

COMPARISON BETWEEN LAB AN D PROPOSED TOOLRESULTS.

CONDlJCTED EM1 GENERATED BYFREQUENCY

RESULTS OF THE

LAB'S RI3ULTS PROPOSED TOOL

120 109.3

IS0

VII. ACKNOWLEDGMENTS

The authors gratefully acknowledges the support of theBrazilian agency FAPERGS for their financial suppolt to thiswork.

I* ,I'"r*U'

Fig. 10- EM1 filter attenuation.

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VIII. CONCLUSIONS

The presented tool is very important to the development ofprojects of conducted EM1 filter, reducing the steps of cut-and-trial that normally are used to solve conducted EM1problems.

This tool can contribute to the reduction of the product

development time, reducing this way, the cost ofdevelopment and providing a quick retum of investments,with the advantage that the product can be sold before thesimilar product of the competitor are on the market.

In the research, this software helps the development ofmore efficient and suitable converters according to theinternational standard rules and the consumer market.Besides of this, the software is also very helpful to teach thePower Electronic discipline.

The simulation time is short, if considered that thesofiware executes thousands of interactions, converging tothe values with an acceptable precision a nd running complexequations at the same time.

IX. REFERENCES

[ I ] Hewlett Packard. EMC In The European Environment -Seminar, Proceedings, Aug 1992, p. 103

[2] F. S. Dos Reis, I. Sebastian, J. Uceda, “Determination ofPFP EM1 Emission by Design”, IEEE Pow er Electronics

Specialists Conference - P E S C W , Aug 1994, pp. 11 17 -1126

[3] CISPR 16 - Specification for Radio InterferenceMeasuring Apparatus and Measurement Methods,second edition 1987.

[4] Albach, M., “Conducted Interference Voltage of AC-DCconverters”, IEEE Power Electronics Specialists

Conference - PESc‘86, pp. 203 - 212.[5] D.S.L. Simonetti, I. Sebastian, F.S. Dos Reis and J.

Uceda, “Design Criteria for Sepic and Cu k Converters asPower Factor Preregulators in Discontinuous ConductionMode”, IEEE Industrial Electronics Society Conference

1992, IECON 92, pp. 283 - 288.[6] K. H. Liu and Y. L. Lin, “Current waveform distortion in

power factor correction circuits employingdiscontinuous-mode boost converters”, IEEE Power

Electronics Specialists Conference. 1989. PESC ‘89Record., 20th,pp. 825 -829 v01.2

[7] V. Vlatkovic, D. Borojevic and F. C. Lee: “Input FilterDesign for Power Factor Correction Circuits”, IEEE

Industrial Electronics Society Conference 1993,IECON’93, pp. 954-958.

[8] Zhang, Y.F.; Yang, L.; Lee, C.Q.; Applied PowerElectronics Conference and Exposition, 1995. APEC ‘95.Conference Proceedings 1995, Tenth Annual Issue: 0 , 5 -

9 M arch 1995. pp. 274 -280, vol.1[9] M. V. Ataide and J. A. Pomilio: “Single-phase Shunt

Active Filter: a Design Procedure C onsidering harmonicsan d EM1Standards”, 1997 ISIE‘97, pp. 422-427.

[IOIG. Spiazzi and I. A. Pomilio: “Interaction between EM1Filter and Power Factor Preregulators with AverageCurrent Control: Analysis and Design Considerations”,Applied Power Electronics Conference and Exposition,1999, APEC’99.

[ I IICISPR 11 - Limits and methods of measurement ofelectromagnetic disturbance characteristics of industrial,

scientific and medical (ISM) radio-frequencyequipment., 2nd edition, 1990.

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art ieee 01- e.f. magnus - tool for conducted em1 and filter design - emi_01

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