Pssive nd Active Hybrid Integrted EMI Filters J. Biel, A. Wirthmueller, R. Wespe, M.. Heldwein, J. W. Kolr Power Electronic Systems bortory Swiss Federl Institute of Technology Zurich, Switzerlnd Emil: biel@lem.ee.ethz.ch E. Wffenschmidt Philips Reserch bortories 5266 Achen, Germny Emil: eberhrd.wffenschmidt@philips.com Abstrct Two new plnr integrted EMI filter structures which reduce the filter volume nd which re bsed on stndrd PCB process technology re presented in this pper. First, pssive integrted EMI filter is presented, which results in volume reduction of 25% compred to the discrete solution. However, this filter requires plnr ferrite core for the CM inductor. In order to eliminte the ferrite core nd reduce the filter volume further (-4% vs. discrete filter) pssive integrted structure is combined with n ctive EMI filtering circuit. The trnsfer function, the volume nd the losses of the discrete nd the two integrted filters, which re designed for 6W PFC converter, re compred. U 1 EMI-Filter i D 1 T 1 C 1 Figure 1: Circuit Digrm of 6W PFC + U 2 I. INTRODUCTION The pursuit of obtining higher power density AC/DC nd DC/DC converters leds to incresing switching frequencies in order to reduce the size of the energy storge elements. These energy storge elements usully influence the overll size of converter significntly. This hs resulted in the development of electromgneticlly integrted structures [1], which combine severl functions in one pssive component. Due to incresing switching frequencies, conducted emissions from 15kHz to 3MHz hve incresed. Thus, the EMI filter hs become lso significnt prt of the converter in terms of size nd cost. For this reson some electromgneticlly integrted EMI filter structures [2] & [4] nd lso ctive EMI filters [5] & [6] hve been proposed. In this pper two new plnr EMI filter structures re presented which llow significnt reduction of the filter volume. These structures re integrted in PCB, which could be mnufctured using cost-sving stndrd PCB mnufcturing process. With the first filter structure ll inductor windings nd ll cpcitors except for lrge differentil mode cpcitor re integrted in the PCB. The cpcitor is relised by prllel connection of X2 SMD-X7R cpcitors. For the lrge inductnce vlue of the CM choke plnr ferrite core is needed. Although, the overll filter hs very low profile (height < 9.5 mm) nd low volume ( 25% volume reduction in comprison to discrete solution). This filter is clled PASSIVE HYBRID INTEGRATED EMI FITER due to the combintion of integrted nd discrete pssive components. In second step the pssive integrted structure is combined with n nlog mplifier (ctive EMI-filter). With the mplifier stge the required inductnce nd cpcitnce vlues of the Tble I: Specifiction of PFC-converter Prmeter Vlue Output Power 6W Output Voltge 41V Switching Frequency 25kHz Input Voltge 11V - 23V (incl. tolernces) (93V - 264V) Input Current 2.6A - 5.5A (incl. tolernces) (2.3A - 6.5A) components decrese significntly, so tht no dditionl ferrite core is needed. The components of the ctive filter re mounted on top of the PCB, in where the pssive filter is integrted. This new pproch results in very compct construction ( 4% volume reduction in comprison to discrete solution) nd is clled ACTIVE HYBRID INTEGRATED EMI FITER. The two proposed filter structures re designed for 6W PFC-converter intended for IT pplictions (cf. fig. 1) with the specifiction given in tble I. In section II of the pper the discrete EMI-filter for the PFC converter is described for compring the new structures with conventionl filter. The structure of the pssive hybrid integrted EMI filter, which is designed nd optimised using FEM simultions, is presented in section III. Therefter, the mode of opertion nd the design of the ctive hybrid integrted EMI filter is explined in section IV. The mesured trnsfer functions of ll three filters together with the losses/efficiency nd the volume re compred in section V. Finlly, conclusion nd topics of future reserch re given in section VI. II. DISCRETE EMI-FITER The discrete EMI filter is designed ccording to the procedure described in [1] nd [11], which is summrised shortly in the following. First, the nd CM conducted emissions of the PFC converter re clculted by simulting high order circuit model including the relevnt prsitic elements. The resulting emission levels re given s exmple in figure 2. There, the blue line describes the simulted emission level mesured by the ISN, the blck curve represents the worst cse mximum vlues inclusive sfety mrgin nd the red und the green line the limits. With the noise nd the regultions on conducted RF emissions for the intended ppliction (CISPR 11) the required ttenution of the filter could be clculted by selecting the lrgest pek vlue within the relevnt rnge (15kHz-3MHz) nd compring this vlue the limits. The required filter ttenution is used to choose n pproprite filter topology [9] nd the number of connected filter stges in series. On the bsis of the filter topology the corner frequency of the filter is clculted, so tht the ttenution is equl to the required one plus 6dB mrgin t the given frequency. With the corner frequency of the filter the C products re given. The filter dmping is - mong other things - determined by n upper limit for the output impednce of the filter. This limit is given by the control loop of the PFC
emission [dbuvrms] 14 12 1 8 6 4 1kHz imits Worst cse incl.. sfety mrgin Simulted noise 1MHz Figure 2: Simulted emission levels of noise, worst cse vlues inclusive 6dB sfety mrgin nd limit vlues. M i n s Common Mode Stges 1.2mH K 1 1.2mH 1nF 4.7Ω Differentil Mode Stges 2µH 4µH 4.7Ω C 1nF 1µF Figure 3: Circuit digrm of the discrete EMI-Filter converter, since the output impednce influences the stbility of the system. Now, the filter topology for the, the corner frequencies nd the required dmping re known. Depending on the number of filter stges nd the topology there re some degrees of freedom for the choice of the component vlues. These degrees of freedom re used to minimise the overll volume of the EMI-filter. As with noise, the required ttenution for the CM could be clculted from CM noise simultion nd given limits. With the required ttenution the filter topology is selected nd the corner frequency of the filter is clculted. Since the Y-cpcitors size is limited by the regultions - the current to ground must not exceed 3mA t 5Hz - the vlue of the inductnce is determined for Y-cpcitors vlues close to the mximum llowed ones ccording to electricl sfety regultions. In order to dmp the CM filter properly some resistors in series with the cpcitors re dded. The resulting filter topology nd the component vlues re shown in figure 3. For the common mode choke Vitroperm T M from Vcuumschmelze hs been chosen in order to minimise the inductor volume. The mesured insertion loss of the discrete filter is given in figure 4 nd the design of the filter is shown in figure 5 nd the overll volume is 47.4cm 3 (48mm 38mm 26mm). In Insertion loss [db] -2-4 -6-8 CM -1.1 1 1 1 Frequency [MHz] Figure 4: Insertion loss of the discrete EMI-Filter o d Differentil - Mode Chokes Differentil - Mode Cpcitor Dmping Resisitors (Bottom Side) Differentil -Mode Cpcitors Common- Mode Choke Common-Mode Cpcitors Figure 5: Photo of the discrete EMI-Filter the next step integrted filters with comprble performnce re designed. III. PASSIVE HYBRID EMI FITERS In order to reduce the filter volume nd simplify the mnufcturing the discrete EMI filter components re - if possible - integrted into PCB, which could be mnufctured with stteof-the-rt PCB process technology. The circuit digrm of the pssive hybrid integrted EMI filter is shown in fig. 6() nd the filter prmeters re given in tble II. In comprison to the discrete filter the inductors re rrnged symmetriclly in the lines nd the inductnce vlue is slightly lrger. This results in smller CM cpcitors (1nF / 8nF insted of 1nF / 1µF) for the sme corner frequency of the filter. The ssembly of the pssive hybrid filter is shown in figure 6(b). Ech of the coupled inductors is integrted by four 15µm copper lyers, which re connected in prllel in order to minimise the ohmic losses. The copper lyers re covered on both sides by 1.25mm thick lyer of 351 (Epcos). Ech coil consists of 17 turns, which re rrnged t the edge of the 8mm 8mm PCB. The totl width of the coils is 2mm. Thus, there is 4mm by 4mm lrge region in the centre of the bord where the winding of the CM choke could be integrted s shown in figure 6(b). Due to the lrge CM inductnce plnr EP 32 core is used for the CM inductor. The coils use two nd one µ-metl (VAC) lyer s mgnetic pth. The dmping of the pssive integrted filter minly results from the frequency dependent resistors which represent the high frequency losses of the coils due to skin- nd proximity effect. The geometry of the coils is designed so tht the DC losses re low but the high frequency losses re high enough to dmp the filter. The dmping elements t the input nd output of the filter remin in order to ttenute oscilltions cused by the line or the input impednce of the converter. The cpcitors nd the resistors of the dmping elements could lso be integrted in the PCB using dielectric nd resistive lyers (e.g. HiK T M -mteril nd OHMEGA-PY / Crbon Pste respectively). In order to simplify the testing of the filter the cpcitors nd resistors of Tble II: Prmeters of the pssive hybrid EMI filter Prmeter Vlue Inductnce 182 µh Number of turns 17 Coupling fctor.86 oss in choke 17.8 W CM Inductnce 1.5 mh Number of turns 16 oss in CM choke 8.4W Size [mm] 8 8 7.2 Boxed volume 46.1 cm 3
M i n s 1.5mH 3.4µH 182µH 1nF C 8nF () Circuit digrm of pssive integrted -Coil CM-Coil (b) 4-lyer PCB for 1 Coil / 1 / 2 CM-Coil Mgnetic-yer 2 nd Coil -4 yers Mid-yer µ-metl Isoltion Copper- Trcks 4 yers in Prllel for 1 st Coil EP 32 - Core Common-Mode Choke (c) yer stck of pssive integrted filter o d section with two prllel lyers ech). The ssembly of the coupled coils consists of the following five different lyers: Mgnetic lyer t the top (e.g. Mg-m,, µ-metl) - thickness: 1mm Winding of coil 1 consisting of one or more copper lyers connected in series nd/or prllel Thin lyer ( 1 µm) of mgneticlly nd electriclly conductive µ-metl T M (comprble to silicon steel) Winding of coil 2 (usully sme design s coil 1 but reverse winding direction) Mgnetic lyer t the bottom (sme s t the top) In figure 7() the current nd the flux direction in the coils for differentil mode excittion is shown. The current in the upper coil cuses the mgnetic flux Φ 1 nd the current in the lower coil Φ 2. In the µ-metl lyer in the middle both fluxes cncel ech other (dshed lines) so tht there is no flux in the µ-metl lyer for symmetric design under excittion. Consequently, the vlue of the inductnce of the integrted coils is independent of the size of the µ-metl lyer. In figure 7(b) the current direction nd flux distribution for CM excittion is given. Due to symmetry resons the common mode flux of both coils Φ CM1 nd Φ CM2 dds up nd flows in the middle between the two coils through the gp nd the µ-metl lyer. The shorter the gp is the lower is the mgnetic reluctnce of the pth nd the higher is the CM inductnce. The rtio between nd the CM inductnce vlues defines the coupling between the two coils (the lrger CM / the lower is the coupling). This reltion is controlled by the horizontl extension of the µ-metl lyer. If this lyer strts t the very left side nd ends t the very right side of the coil the coupling is pproximtely zero. In figure 8 the dependence of the coupling fctor k on the length of the µ-metl lyer is shown for test ssembly. These results hbe been obtined by the developed design procedure (described lter) nd re vlidted by mesuring the coupling coefficient for different extensions of the µ-metl lyer. Since the CM current / flux hs lmost no spectrl components below the switching frequency the mplitude of the CM flux is smll. Therefore, the µ-metl lyer, which hs sturtion flux density of pproximtely.8t, could be very thin ( 1µm). In [12] the distributed cpcitnce between winding nd conductive lyer is trnsformed into network consisting of three cpcitors (cf. fig. 9). The cpcitnce C is the sttic cpcitnce between the winding nd the conductive lyer (cf. [13]). As the equivlent cpcitnce prllel to the winding is negtive it could be used to cncel the prsitic cpcitnce C P of the winding (cf. [8] nd [4]). Thus, the distributed cpcitnce cused by the µ- Metl lyer could be used to reduce the vlue of the cpcitnce ) I1 (d) Photo of ssembled pssive filter I1 µ-metl Φ 1 Φ 2 Coil 1 Coil 2 Figure 6: Circuit digrm (), photo of PCB (two re need for the pssive filter) (b), lyer stck (c) nd photo of ssembled pssive hybrid filter (d). b) Copper Trcks the dmping network re relised by SMD components in the prototype. A. Design of Coupled Inductors The symmetriclly rrnged inductors re implemented by two coupled inductors. In figure 7 the principle of opertion is shown for () nd CM (b) excittion is shown (PCB cross Φ CM1 µ-metl I2 Copper Trcks ΦCM2 I2 Figure 7: () Digrm of coupled coils (b) design of the coils. Gp Coil 1 Coil 2
Coupling coefficient 1.8.6.4.2-5 -4-3 -2-1 1 2 3 Gp of µ-metl lyer [mm] Figure 8: Dependence of the coupling fctor k on the length of the µ-metl lyer (cf. figure 7) - mesured vlues t. in prllel to the winding nd to increse the frequency of the first resonnce of the coil if the lyer is connected to ground. The vlue of the sttic interlyer cpcitnce C is clculted within the design procedure nd djusted by vrying the verticl distnce between the µ-metl lyer nd the winding. With the construction shown in figure 7, where the CM flux flows through the µ-metl lyer in the middle, the inductnce is lrger thn or equl to the CM inductnce due to the coupling of the flux. If lrger CM inductnce nd lower inductnce is needed, the winding direction of one coil hs to be chnged. In this cse thicker mgnetic middle lyer (twice the thickness of the outer mgnetic lyer) is needed, becuse the reltively lrge flux flows through the middle lyer. The chievble mximum vlues for the CM nd the inductnces re the sme for both design possibilities, if the distnce between two mgnetic lyers bove nd below one PCB (i.e. the gp) is the sme. Consequently, the design with the chnged winding direction leds to n incresed volume nd lrger mgnetic losses for the sme mximum chievble inductnce vlues nd should only be used in cse CM inductnce is needed, which is lrger thn the one. B. Design Procedure The integrted inductors of the EMI-filter re designed using n utomted design procedure, whose flow chrt is given in figure 1. This procedure, which is bsed on finite element simultions (COMSO T M ) nd nlytic clcultions, will be shortly explined in the following. At the beginning of the procedure different prmeters like the number of lyers in the PCB N, the number of prllel connected lyers N P, PCB size B T, the verticl distnce between the lyers t ν, etc. must be specified by the user. These prmeters re not vried within the design procedure since they minly depend on requirements not relted to the filter itself. On the other hnd, there re prmeters like the number of turns N, the PCB width w T rck nd distnce w T rck, the thickness t C of the mgnetic lyers, etc. which could be vried in order to optimise the design. With the prmeters given in MATAB T M input-files for FEM simultions describing the geometry nd boundry conditions re utomticlly generted by the progrmme. In the next step FEM simultions re crried out by the progrmme for different setups (CM- nd excittion, different voltge distributions)- cf. figure 11. On the bsis of the mgnetic nd electric energies the inductnce nd cpcitnce vlues re clculted. Furthermore, the mgnetic field distribution is used to clculte the HF resistnces of the coils nlyticlly. Therefter, the C P C C U 1 U 2 U 1 2 CP 2 U 2 C 6 Figure 9: Equivlent network for distributed cpcitnce between winding nd conductive lyer ccording to [12] Fixed Prmeters N / N P / BxT / t ν µ/ε / I /I CM Vrible Prmters N / w Trck / d Trck / d CO / t C m-file COMSO Input-file / Geometry I CM /I distribution Mgnetic field distribution Energy & CM H-Field HF-osses Voltge distribution Electric field distribution Energy Cpcitnces Equivlent Circuit for & CM C 1 k C C 9 5 C 3 C 4 C7 C 8 C 6 C 2 C 1 n potentils Figure 1: Flowchrt of the design procedure for the integrted coils. Air Trcks ine of symmetry flux Bredth of µ-metl lyer µ-metl lyer Air Coil 1 Coil 2 Figure 11: -Finite element simultion of pssive hybrid integrted EMI filter. clculted vlues re trnsformed into equivlent circuit vlues of the EMI filter. The described design routine offers the possibility to be used within n optimistion routine, which vries for exmple the number of turns nd the design of the trcks in order to minimise the filter volume or to mximise the efficiency. IV. ACTIVE HYBRID EMI FITER The discrete nd lso the pssive hybrid EMI filter require lrge common mode inductnce becuse the vlue of the Y- cpcitnce is limited by regultions nd becuse the corner frequency of the filter must be low due to the CM emission level. Since the mplitude rtio of the high frequency CM current nd the current t the line frequency is usully reltively smll, the volume of the CM inductor could be reduced by using n ctive filter. This ctive EMI filter consists of two smll common mode inductors, two 2nF cpcitors, mesurement network nd n nlog mplifier s shown in figure 12() (cf. [14]). With the mesurement network the CM voltge V CM cused by the converter/lod is mesured vi the two 1nF cpcitors. The CM voltge is mplified by n nlog Clss-A mplifier, which injects n inverted CM current vi the two 22nF cpcitors into the filter network. Thus, the CM current resulting from the lod Optimistion of geometry for miniml losses / size
Tble III: Mterils for Cpcitnce Integrtion C-m HiK Rogers Permittity 11 1.2 Brekdown Voltge 3kV/mm 1kV - tn δ.2.2.27 Cpcitnce per cm 2.2nF.2nF.2nF is cncelled/reduced by the ctive filter. Due to the limited gin of the mplifier nd non-idel components the mplitude of the CM voltge/current is only reduced by pproximtely 2dB in best cse. Moreover, the limited bndwidth of the mplifier requires reduction of the gin t higher frequencies in order to gurntee the stbility of the system. This lso results in decline of the CM voltge/current cncelltion t higher frequencies. In the limited frequency rnge from pproximtely 1 khz up to 6 MHz, where the voltge/current cncelltion is working, the effective CM cpcitnce is incresed very much by the mplifier. Thus, smller CM inductnce cn be used to obtin the sme corner frequency / ttenution s for the CM filter of the discrete/pssive hybrid filter. The decline of the ttenution due to the limited mplifier bndwidth is not criticl, becuse lso the effective impednce of lrge common mode choke decreses with incresing frequency due to the prsitic cpcitnce which cuses prllel resonnt behviour of the choke t higher frequencies. The two common mode inductors needed for the ctive EMI filter re integrted in the PCB s described in the previous section. The finl design of the complete ctive hybrid integrted filter is shown in figure 12(b). There, the components of the Terminl µ-metl PCBs () Picture of ctive filter HF - Amplifier One Coil (b) PCB of one lyer Cpcitors Integrted Coils (c) 3D drwing of finl ssembly of ctive filter Figure 13: () Picture of ssembled ctive hybrid EMI filter (b) Picture of the PCB of one lyer. Tble IV: Prmeter of Active Hybrid EMI-filter Prmeter Vlue Inductnce 216 µh CM Inductnce 53 µh osses 28.4 W Size [mm] 6 6 16.2 Volume 27.3 cm 3 M i n s 1Ω 1Ω Coil 1 Coil 2 18µH 26.5µH 26.5µH 18µH 22nF C 1nF C 82nF 8nF 1Ω 1nF 22nF 3V 1Ω Mesurement Ampl. / Feedbck V CM Network -3V Active EMI Filter () Circuit Digrm of ctive hybrid Active EMI - Filter C Coil 1 I 3 I 4 o d ctive filter re mounted on top of the PCB. Below the ctive filter the cpcitnces for mesuring the CM voltge nd injecting the CM current s well s the reltively smll cpcitnces for dmping resonnces t the input nd the output of the filter cn be integrted. Due to the plnr design these cpcitors show low ESR nd ES. In tble III some dielectric mterils for integrting cpcitnces into PCBs re shown. Due to the reltively low permittivity of these mterils the lrge cpcitors for the differentil mode C still hve to be relised s SMD cpcitors which re mounted on top of the PCB besides the ctive filter components. In figure 13() the exmined prototype of the coupled coils for the ctive filter is shown. It consists of four lyers of 32 from Epcos with thickness of pproximtely 1.3mm, four PCBs ech with four 15µm lyers of copper for the coils (cf. fig. 13(b)) nd two lyers of µ-metl. At the left hnd side the terminls of the µ-metl lyers re shown with which the lyers could be connected to ground in order to reduce the prsitic cpcitnce. Below the pictures 3D drwing of the finl ssembly of the integrted ctive hybrid filter is shown in figure 13(c). In tble IV the technicl prmeters of the ctive EMI-filter re listed. Coil 2 (b) Construction of ctive hybrid filter Figure 12: () Circuit digrm of the ctive hybrid integrted EMI-filter (b) Design of the ctive hybrid integrted EMI-filter. I 3 I 4 V. COMPARISON OF THE EMI-FITERS In order to compre the performnce of the different filters mesured trnsfer functions, losses nd volume of the discrete, the pssive nd the ctive hybrid filter re presented in the following. Usully, insertion loss mesurements, i.e. the rtio U 2/U Noise, re used to chrcterise EMI filters. However, these mesurements lso include the ttenution which results from the source impednce of the mesurement circuit (usully 5Ω) nd the filter cpcitors (cf. fig. 14). The source / internl impednce of
Tble V: Clculted nd mesured prmeters of the three compred EMI-filters Prmeter Discrete Pssive Filter Active Filter Filter clculted mesured modified clculted mesured modified Inductnce 6 µh 194 µh 182 µh 26 µh 132 µh 18 µh 15 µh CM Inductnce 1.2 mh 1.45 mh 1.5 mh 1.45 mh 65 µh 53 µh 73 µh osses @ 7.7A p 3.56 W 2x(7.6+3.7)W 2x(8.9+4.2)W 2x(2.2+3.7)W 4x5.7W+6W 4x7.1W+6.1W 4x1.6W+6W Efficiency @11V 99.4 % 96.2 % 95.6 % 98 % 95.2 % 94.3 % 98 % Efficiency @23V 99.8 % 99.1 % 99. % 99.5 % 98.1 % 97.9 % 98.8 % Totl Volume 47.4 cm 3-36.1 cm 3 27.4 cm 3-27.3 cm 3 21.3 cm 3 the noise source nd with tht lso the dditionl ttenution depend very much on the converter topology nd the design of the converter. In order to obtin informtion bout the filter ttenution which is independent of the source impednce, the trnsfer function, i.e. the rtio U 2/U 1, is used in the following. The input voltge of the filter U 1 for given source impednce could be clculted with the input impednce Z IN of the EMI filter, which is lso presented in the following. The dditionl ttenution becuse of the source impednce could be seen in figure 15, where the insertion loss nd the trnsfer function for the ctive filter re plotted in the sme grph. In figure 16 the CM nd the ttenution nd the input impednce of the pssive hybrid filter is given. There, the two curves for the CM show the different ttenution of the filter when the µ-metl lyer is connected to ground or free floting. Due to the dditionl prsitic cpcitnces (cf. fig 9) the HF behviour of the filter is improved. The resonnt pek of the CM ttenution between 4kHz nd 5kHz results from the chrcteristic frequency of the CM choke. Due to the lrge source impednce of the PFC converter (boost inductor: 187µH - cf. fig. 1) the ttenution of the pssive filter increses very much in the frequency rnge from 1kHz to 1MHz, since the input impednce of the filter is reltively low in this region. For exmple, t 1kHz pproximtely dditionl 2dB result from the lrge source impednce resulting in n effective ttenution lrger thn 4dB for t 1kHz. In the considered frequency rnge, the input impednce of the ctive filter for is even lower thn the one of the pssive filter, wht leds to lrger dditionl dmping due to the source impednce (cf. fig. 17). Consequently, the ttenution of the two integrted filters is comprble to the one of the discrete U Noise 5Ω U 1 Z IN Tested Filter HF-Trfo 5Ω Figure 14: Circuit for the mesurement of the trnsfer (U 2 /U 1 ) function (filter ttenution) nd the input impednce. Attenution [db] -2-4 -6-8 -1 1k ttenution insertion loss U 2 1M 1M 3M Figure 15: Comprison between the ttenution / trnsfer function (U 2 /U 1 ) nd insertion loss of the ctive hybrid filter. Attenution [db] Impednce [Ω] -1-2 -3-4 -5-6 -7 1k 1k 1k 1 1 1.1.1 1k CM w/o GND CM w. GND 1M 1M 3M () Trnsfer function of ctive filter CM 6 3 3 6 9 1-33 -67 1 1k 1M 1M 3M (b) Input impednce in CM & Figure 16: () Trnsfer function of the pssive filter for CM with (w. GND) nd without connection of the µ-metl lyer to ground (w/o GND) nd for. (b) Input impednce of the filter t the lod side for CM nd for with phse (dshed lines). 67 33 Phse [degree] filter nd even exceeds it bit. The comprtively low resonnce frequency of the CM choke of the pssive integrted filter results in CM ttenution curve which is not s good s the one of the discrete filter. The reson for this re the prsitic cpcitnces resulting from the plnr winding design. A new design of the CM choke, which leds to reduced prsitic cpcitnces nd lso lower losses, is shown in figure 18. There, the core is integrted in the PCB by mgnetic lyers nd the winding consists of wire or in cse of low power pplictions of PCB trcks. This design will be evluted nd the results presented in future pper. In figure 17() the CM ttenution of the ctive integrted filter is shown. There, it could be seen tht the mplifier results in n dditionl ttenution of 15-2dB in the frequency rnge from 4kHz to 4MHz. The resonnt pek t pproximtely 16kHz is cused by the limited gin of the mplifier. As simultions show the gin could be incresed by using trnsistors with higher trnsition frequency in the power stge of the mplifier. The improved behviour will lso presented in future publiction. The resonnt pek round 2MHz in the CM ttenution of the ctive integrted filter is cused by the chrcteristic frequency of the integrted coils. Phse [degree]
Attenution [db] Impednce [Ω] Impednce [Ω] 2-2 -4-6 -8-1 1k 6 5 4 w. AMP 3 2 1 1k 1 1 1.1.1 1k CM w/o Amp CM w Amp 1M 1M 3M () Trnsfer function of ctive filter CM w/o AMP 9 6 3 3 6 9 1k 1M 1M 3M (b) Input impednce in CM 1k Impednce -1 1k 1M 1M 3M (c) Input impednce in 1 5-5 Phse [degree] Figure 17: () Trnsfer function of the ctive filter for CM with (w. AMP) nd without Amplifier (w/o AMP) nd for. (b) Input impednce of the filter t the lod side for CM with (w. AMP) nd without Amplifier (w/o AMP) with phse (dshed lines) (c) Input impednce of the filter t the lod side for with phse (dshed lines). Cpcitors PCB Mgnetic yer Winding Figure 18: New design of the CM choke. In tble V the volume, the losses nd the efficiency of the three EMI filters re given. The vlues in the modified columns result from using Vcoflux 48 (VAC), which hs sturtion flux density of 2T, insted of 351/32 s mgnetic lyer. As cn be seen the losses nd the volume of the integrted filters cn be reduced very much so tht the efficiency of the integrted filters Phse [degree] is comprble to the one of the discrete filter but the volume is reduced by lmost 5%. VI. CONCUSION The EMI filter is significnt prt of converter in terms of size nd cost. Thus, the size of EMI filters must be reduced nd the mnufcturing simplified in order to increse the power density nd to reduce the cost of converter systems. In the pper design procedure nd mesurement results for two different integrtion pproches - pssive hybrid integrtion in PCB nd n ctive hybrid integrtion with n ctive EMI filter - re presented. The filter re integrted into PCB bord which could be mnufctured with stndrd PCB mnufcturing technology. Due to the integrtion the filter volume is reduced up to 4% while mintining high efficiency. REFERENCES [1] J.T. Strydom, Electromgnetic Design of Integrted Resontor- Trnsformers, Ph.D. Thesis, Rnd Afrikns University, South Afric, 21. [2] J.D. vn Wyk, F.C. ee, Z ing, R. Chen, S. Wng nd B. u, Integrting Active, Pssive nd EMI-Filter Functions in Power Electronic System: A Cse Study of Some Technologies, Power Electronics, IEEE Trnsctions on, Volume 2, Issue 3, My 25, Pge(s):523-536. [3] E. Wffenschmidt, B. Ackermnn nd J.A, Ferreir, Design method nd mteril technologies for pssives in printed circuit Bord Embedded circuits, Power Electronics, IEEE Trnsctions on Volume 2, Issue 3, My 25, Pge(s):576-584. [4] R. Chen, J.D. vn Wyk, S. Wng nd W. G. Odendl, Improving the Chrcteristics of Integrted EMI Filters by Embedded Conductive yers, Power Electronics, IEEE Trnsctions on, Volume 2, Issue 3, My 25, Pge(s):611-619. [5] T. Frks nd M.F. Schlecht, Vibility of Active EMI Filters for Utility Applictions, Power Electronics, IEEE Trnsctions on, Volume 9, Issue 3, My 1994, Pge(s):328-337. [6]. white nd M.F. Schlecht, Design of Active Ripple Filters for Power Circuits Operting in the 1-1MHz Rnge, Power Electronics, IEEE Trnsctions on, Volume 3, Issue 3, July 1988, Pge(s):31-317. [7] T.C. Neugebuer nd D. J. Perrult, Filters With Inductnce Cncelltion Using Printed Circuit Bord Trnsformers, Power Electronics, IEEE Trnsctions on, Volume 19, Issue 3, My 24, Pge(s):591-62. [8] T.C. Neugebuer nd D. J. Perrult, Prsitic Cpcitnce Cncelltion in Filter Inductors, 35 th IEEE Power Electronics Specilists Conference, PESC 4, Achen, Germny, June 24, Pge(s):312-317. [9] M.J. Nve, A Novel Differentil Mode Rejection Network for Conducted Emissions Dignostics, IEEE 1989 Ntionl Symposium on Electromgnetic Comptibility, Denver, USA, 23-25 My, 1989, Pge(s):223-227. [1] M.. Heldwein, T. Nussbumer, F. Beck, J.W. Kolr, Novel Three- Phse CM/ Conducted Emissions Seprtor, Proceedings of the 2th Annul IEEE Applied Power Electronics Conference nd Exposition, Austin (Texs), USA, Mrch 6-1, Vol. 2, 25, Pge(s):797-82. [11] T. Nussbumer, M.. Heldwein, J.W. Kolr, Differentil Mode EMC Input Filter Design for Three-Phse Buck-Type Unity Power Fctor PWM Rectifier, Proceedings of the 4th Interntionl Power Electronics nd Motion Control Conference, Xin, Chin, Aug. 14-16, Vol. 3, 24, Pge(s):1521-1526. [12]. Oestergrd, Modelling nd Simultion of the Diode Split Trnsformer, Disserttion, Fculty of Engineering nd Science t Alborg University, 1999, Pge(s):139-169. [13] J. Biel, J.W. Kolr, Using Trnsformer Prsitics for Resonnt Converters - A Review of the Clcultion of the Stry Cpcitnce of Trnsformers, Conference Record of the 25 IEEE Industry Applictions Conference 4th IAS Annul Meeting, Hong Kong, Chin, Oct. 2-6. [14] M.. Heldwein, H. Ertl, J. Biel nd J. W. Kolr, Implementtion of Trnsformer-ess Common Mode Active Filter for Off-line Converter Systems, Proceedings of the 21th Annul IEEE Applied Power Electronics Conference nd Exposition (APEC), Dlls (Texs), USA, Mrch 19-23, 26.