Computer Aided Design and Modeling of High Frequency Magnetic Components *

Transcription

1 Computr Aidd Dsign and Modling of High Frquncy Magntic Componnts * B. Bckr H. Grotstolln Univrsity of Padrborn, FB 14 Powr Elctronics and Elctrical Drivs Pohlwg Padrborn, Grmany Tl. : 0049/5251/ FAX : 0049/5251/ mail: bbckl@pbla.uni-padrborn.d L. Hinmann ABB Corporat Rsarch Cntr DECRC/Vl, Powr Elctronics Spyrr Str Hidlbrg, Grmany Tl.: 0049/6221/ FAX.: 0049/6221/ mail: hinmann@qmgat.dcrc. ab b.d Abstract Hnc, in most cass th dvlopmnt of convrtrs and invrtrs follows an itrativ procdur. For this rason A nw computr-aidd dsign program is prsntd suita- CAD-programs ar usd to nhanc th fficincy of th bl for dsign, optimization and modling of high frqun- whol dvlopmnt procdur. cy multiwinding transformrs and inductors in any powr n th first dvlopmnt stp CAD-programs ar usd to lctronics applications. Dpnding on th arrangmnt support th rough dsign of th componnts according to of th windings and dh ambint tmpratur on on hand th rquirmnts of th application aftr th circuit was th wanding losss and th cor losss can b calculatd chosn. Howvr, in ordr to acclrat this first dsign if th voltag and currnt wavforms at th trminals ar stp ths CAD-programs ar oftn writtn by th usr known in principl. On th othr hand stat spac modls himslf. Unfortunatly in most of all cass such CADor quivalnt circuits of diflrnt accuracy can b dtrmi- programs cannot b usd for high frquncy powr lcnd and implmntd asily into simulators lik SABER. tronics applications, bcaus th skin ffct insid of th An optimization routin allows th intractiv optimizati- magntic componnts and th cor losss cannot b consion of hzgh frquncy magntic componnts rgarding los- drd with sufficint accuracy, s [l] and [2] as xampls. ss, wzght or hight. Thrfor,.g. in [3] a high frquncy transformr dsign and loss calculation program was prsntd. With this program th winding losss can b calculatd approxima- 1 ntroduction tly dpnding on th winding arrangmnt by using th Th dvlopmnt of convrtrs and invrtrs in high fr- Fourir-sris mthod. Th cor losss can b dtrmiquncy powr lctronics applications is always tim and nd approximatly basd on mpirically drivd cor loss cost consuming bcaus quations. Additionally th tmpratur of th transformr can b calculatd by mans of simpl thrmal modls. 0 in gnral voltags and currnts of all componnts Unfortunatly, th accuracy of th rsult dpnds mainof th powr train show mor than on frquncy ly on th xact wavforms of th currnts and voltags componnt, at th trminals of th dvic which hav to b known in advanc. 0 parasitic quantitis lik lakag inductancs of com- Howvr, th quality of this information can b improvd mutation circuits, ffcts Of diods and parasitics of smiconductor switchs influnc th oprational bhaviour of th complt powr lctronic circuitry and 0 th skin ffct insid th windings of high frquncy transformrs and rsonant inductors hav to b considrd and avoidd by a propr dsign. *This work is sponsord by a rsarch contract with ABB CEAG, Stromvrsorgungstchnik, Snator-Sdiwartz-Ring 26, Sost, Grmany by simulations of th complt powr train. Thrfor, in th scond stp oftn th rough dsign is chckd by circuit simulations bfor th first brad board circuit is built. For this task powrful commrcial simulators lik SPCE or SABER ar availabl on th markt. Howvr, it is wll known, that th accuracy of th simulation rsults dpnds strongly on th dvic modls which ar usd to dscrib th larg signal bhaviour. For that rason on on hand many fforts hav bn mad in ordr to improv th modls of powr smiconductors. On th othr Xi95 $ EEE

2 ~ hand although physically basd high frquncy multiwinding transformr and inductor modls wr prsntd in prvious publications, s [5], [4], [6] and [7], up to now such modls ar not availabl in commrcial simulators. Th rason for that may b found in th difficultis to undrstand th complx modling quations and to nabl a computr-aidd spcification of various winding arrangmnts and cor gomtris. Th nw computr-aidd dsign program prsntd in this papr allows a computr-aidd dsign, optimization and modling of high frquncy multiwinding transformrs with sid by sid or planar windings basd on th analysis givn in [6] as wll as of high frquncy inductors as rportd in [7]. Additionally, th dsign and th intractiv optimization of th powr train of complt switchd mod powr supplis is availabl as a spcial fatur. n this cas th dsign procdur is following a strss analysis prsntd and outlind in [9]. Howvr, th accptanc of such a program by dvlopmnt nginrs and scintists in industry and rsarch is dtrmind by th fact, that th program will b an intgratd part of.g. commrcial simulators or othr complx dsign tools. For this rason th primary objctivs for th dvlopmnt of this larg CAD-program ar th following: 2 8 Portability on diffrnt hardwar platforms. Offring a usr frindly mnu guidanc. Th stup of gnral and simply xtndabl libraris for algorithms and componnts. A modular structur of th total program to xtnd moduls in a simpl way. ntrfacs to othr programs.g. to commrcial simulators lik SABER. Structur and Potntials of th nw CAD-Program Th complt structur of th modular CAD-program is givn in figur 1. Th individual subprograms ar linkd by a main program so that a bidirctional dataflow btwn th diffrnt subprograms can b guarantd. All rquird mathmatical algorithm.g. for invrsions or transposion of matrizs, quivalnt stat spac transformations or sarching for roots ar collctd in th algorithm sublibrary. Th componnt library is dividd into furthr sublibraris which contain th data of diffrnt cor gomtris and cor matrials, conductor typs and conductor matrials, powr diods, powr transistors and capacitors. Th cor sublibrary contains all rlvant data of narly all common cor gomtris for sid by sid and planar windings and in addition all rlvant data of svral various non common customr mad cor gomtris. t should also b notd, r > r > Output ntrfac Usr ntrfac Library t (Simulaton, Law-Writr, plottr a.0.) t Program-Krnl (Coordination of data, projct-managmnt) Dsign and Opimization of Switchd Mod Powr Supplis Modling Figur 1: Complt structur of th nw CAD-program that for all cor gomtris a simplifid thrmal modl is availabl so that th actual tmpratur ris can b calculatd approximatly dpnding on th ambint conditions (.g. natural or forcd air cooling). Th conductor library contains data of all solid round wirs following DN , foil conductors of various hights and arbitrary widths as wll as high frquncy litz wir. Th strss analysis.g. givn in [9] rprsnts th basis for th dsign and intractiv optimization of switchd mod powr supplis. Hnc, th program allows an almost automatd dsign of all componnts of th powr train of svral switch mod powr supplis in hard and soft switching tchniqu. All ncssary spcifications lik input voltag rang, output voltag, output voltag rippl at stady stat, output currnt rang, maximum ambint tmpratur as wll as cooling typ hav to b dtrmind by th usr. Additionally, th switching frquncy can b varid by th usr intractivly in ordr to obtain a loss, wight and cost minimizd switchd mod powr supply. Thus, a computr aidd comparison of diffrnt switchd mod powr supplis can b prformd asily and th bst suitd topology orland th bst suitd switching tchniqu will b slctd by th program. This optimization procdur will lad to a drastically rducd tim and cost intnsiv prototyping phas. Additionally, it should b notd, that th usr frindly CAD-program is availabl as PC-vrsion undr MS Windows 3.1. Th portability of th CAD-program to diffrnt oprating systms is guarantd by th us of th standardizd programming languag ANS-C and th sparation into diffrnt moduls. Now, in ordr to xplain th potntials of th complt program in figur 2 th flowchart of th CAD-program is shown rprsntd by blockdiagrams. nsid th block program-krnl th spcifications can b rad from a fil or - if a nw projct is startd - th spcifications hav to b ditd by th usr. 336

3 and dsignd topology is dsird, all magntic componnts can b modld in th block modling by th proposd mthods prsntd in [4], [6] and [7]. Th gomtry paramtrs of th magntic componnts ar usd dirctly in ordr to crat a subcircuit or a tmplat. This will b don automatically by th program. Finally a complt ntlist will b gnratd by th usr and th simulation can b startd. t is important to not, that th block modling can b usd as a sparat program. Thus, th modling of magntic componnts is not limitd to a spcial kind of switchd mod powr lctronics applications. This will xplaind in dtail in th nxt sction. 3 Modling stps of high frquncy magntic componnts Th following dscription of th diffrnt modling stps of magntic componnts rfrs only to th block modling of th complt CAD-program. Hnc, in ordr to start th high frquncy multiwinding transformrs or inductors modling algorithm it is assumd, that all rquird maximum ratings lik ambint tmpratur, ma. allowabl tmpratur ris of th magntic componnts during opration or max. allowabl magntic flux dnsity insid th cor wr dtrmind. Additionally, th numbr of turns of all windings hav to b known and a suitabl cor is slctd. Thn th following stps hav to b prformd, subsquntly xplaind for th modling of a transfomr: 0 Dtrmination of th basic winding layout (sid by sid or planar windings). 0 Dtrmination of th numbr of conductor layrs 0 Spcification of all conductor layrs (turns pr layr, conductor matrial and conductor typ) 0 Spcification of all insolation layrs Figur 2: Flowchart of th nw CAD-Program Additonally, th usr has to slct a topology and th switching frquncy. Aftrwards th main mnu is usd as a kind of switching board in ordr to slct all componnts of th powr train of th slctd topology. Thus, in th block dsign and optimization of switchd mod powr supplis all componnts can b dsignd and optimizd using th componnt library of th CAD-program. f th dsign procdur is finishd th usr gts a componnt list with suitabl dsign proposals. Now this part of th program can b lft and th rsults can b usd to dsign a first prototyp. Othrwis th usr can slct.g. anothr topology or/and anothr switching. Thn th dscribd procdur will start again. Howvr, if a simulation of th powr train of th slctd Now in ordr to visualiz this diffrnt prprocssing phas in figur 3 a scrn dump during a layr spcification of a planar transformr is shown. Thn finally th conductor layrs hav to b composd to final windings by sris or paralll connctions. Aftr compltion of th spcifying stag a subroutin controls th spcifications and givs a warning, if.g. unqual numbrs of turns ar composd in paralll connnction or if th complt winding dos not fit into th window ara of th cor. Subsquntly, th modling algorithm is startd and th rsults obtaind can b shown at th computr srn, s figur 4. n this figur th principl winding arrangmnt of th transformr with xcidd winding (markd with E) and th shortd winding (markd with S) as wll as th calculatd short-circuit rsistanc and inductanc in dpndnc of th frquncy is illustratd. Now, th modling algorithm is startd as shown in th blockdiagram of figur

4 constant. Finally th rsults can b chckd by th usr and a prototyp can b dsignd. Othrwis th dsign and modling procdur is rpatd as long as rquird in ordr to obtain a nw suitd dsign. c Start Cor and conductor Figur 3: Scrn dump during th spcification stag Simulator Libraly U Simulation Figur 4: Scrn dump with planar transformr and calculatd short circuit inductanc and rsistanc Aftr th modl lvl is slctd th modl paramtrs ar calculatd and subsquntly a subcircuit or a tmplat is gnratd. Thus, if a multi-lvl simulator lik SABER is usd th usr obtains dirctly a tmplat in th simulator modling languag. Now, th ntlist can b compltd by adding th tmplat or th subciruit to th ntlist of th rmaining powr lctronic circuitry and th simulation can b startd. Howvr, as it will tak a lot of CPU-tim th actual tmpratur of th magntic componnt will not b considrd dirctly during th simulation. For this purpos aftr finishing th simulation in th block Postprocssing th tmpraturs of th magntic componnts can b dtrmind by using th calculatd currnt and voltag wavforms at th trminals of all windings. With th simplifid thrmal modl th actual tmpratur is calculatd and subsquntly th tmpratur will b compard with th start-tmpratur. f th diffrnc btwn ths two tmpraturs is not tolrabl th modl paramtrs of th transformr hav to b calculatd onc mor and th simulation starts again until th tmpratur bcoms narly h Assssmnt Prototyp of rsults Figur 5: Modling stps of high frquncy magntic componnts 4 Vrification Up to now, th CADS-program is usd to dsign and optimiz a lot of high frquncy transformrs and inductors for diffrnt kinds of powr lctronic applications. As first xampl th dsign and th modling of a four winding transformr and a rsonant inductor of a rsonant convrtr with trtiary sidd rsonant capacitor (SPRKT) 338

5 - xplaind in dtail in [lo] - was chosn, s figur 6. GXNQOJO _._.., Figur 6: Circuitry of a rsonant convrtr with trtiary sidd capacitor (SPRCT) (Sl) is shortd and th primary sidd winding srvs for xcitation. Figur 8 shows th short-circuit rsistanc and inductanc. Howvr, it should b notd, that th dviations on th sid of th short-circuit rsistanc ar du to nglcting th short-circuiting branch outsid th cor in th modl. ; :" 10 ' """" ' ' 1 " " " - rs. acc. to [ J b x - Rshl R l: Z K + Now, in ordr to compar calculation and masurmnt rsults th following spcifications had to b mt for this convrtr: Th avrag valu of th controlld output voltag is U2 = 5 /, th max. avrag valu of th output currnt is 12ma = 50 A and th input voltag can b in th rang of 275 V 5 Vi V. Figur 7 shows th principl arrangmnt of th planar windings of th transformr. t - Lshl 1n t\ t \\ x - 10' ' -ckhz Figur 8: Masurd and calculatd short-circuit rsistanc (a) and inductanc (b) of th transformr usd Figur 7: Winding arrangmnt of a transformr usd A hight rducd RM 12-cor from Simns (Matrial N87) is usd for th placmnt of th planar windings. Th thr layrs of both scondary sidd windings (S1 and S2) ar connctd in paralll rspctivly. Both scondary sidd windings wr ralizd with coppr foil of a thicknss of 0.5 mm. Th primary sidd winding (P) and th trtiary sidd winding (T) was mad up by PCBs with a coppr thicknss of 105pm. Th bas matrial has a thicknss of 0.25mm. All primary sidd PCBs and all trtiary sidd PCBs wr connctd in sris rspctivly. Hnc, both windings hav 18 turns and th distribution of th turns can b infrrd from figur 7. As a first rsult figur 8 shows th masurd and calculatd short-circuit rsistanc (a) and inductanc (b) in dpndnc of frquncy, if th first scondary winding Th rsonant inductor consists of an ungappd PQ20/25 cor from TDK with an intrlayr gap of 0.3 mm and of 9 turns of high frquncy litz wir. Masurmnts wr takn in ordr to gnrat a modl of 3'd ordr basd on th modling mthod prsntd in [7]. n cas of th rsonant inductor an quivalnt circuit, s figur 9) was slctd for modling dscription kn Figur 9: Equivalnt circuit of th rsonant inductor of th SPRCT Now, in ordr to dmonstrat th good corrspondnc btwn th masurd and calculatd frquncy rsponc 339

6 of th rsonant inductor, in figur 10 th calculatd and masurd frquncy dpndnt rsistancs of th inductor ar shown. r $ t lo! 1 3 L r R , o4 khz Figur 10: Calculatd and masurd rsistanc of th rsonant inductor in dpndnc of frquncy Sinc th modl paramtrs wr xtractd from th physical inductor which was applid in a circuit drivn at a maximum frquncy of 1.1 MHr, th curvs ovrlap obviously in th considrd frquncy rang, if th quivalnt circuit dpictd in figur 9 rplacs th inductor. Not, that although th xcitation of th inductor is narly sinusoidal th convrtr is controlld in th frquncy rang of 530kHz to 1.1 MHz. Th modl automatically taks car of frquncy modulation control. Simulation rsults and masurmnts of th rsonant convrtr shown in figur 6 ar compard and displayd in figur 11. As xampls th rsonant inductor currnt wavform, th voltag wavform at th trminals of th scondary sidd winding S1 and th voltag wavform at th rsonant capacitor Cr, all at stady stat, ar illustratd. Th simulator SABER was usd including powr diod modls following th proposal of Lauritzn. Ths diod-modls wr paramtrizd by th us of data from shts. Ringing, visibl on masurd rsults ar causd by parasitics. As a scond xampl th dsign of a high currnt transformr in a high dnsity Two-Transistor Forward Convrtr with 5V/200A output is givn. Th convrtr is shown in figur 12 and sinc th spcifications wr alrady prsntd [S in this papr only th rlvant data will b givn. This xampl will b usd to dmonstrat how a optimization of th transformr rgarding losss and wight works and how it can b prformd asily with th nw CADprogram. Now in ordr to optimiz th transformr th winding width was varid intractivly with th program. Starting with an original E-30 Cor from TDK (winding width of appr. 25 mm th winding width was incrasd to mor than 65 mm by adding -pics of frrit matrials in stps of Ab = 5 mm. This is dmonstratd in figur A- (rs Figur 11: Masurd and simulatd voltag and currnt wavworms of th SPRCT 13 in principl. n ordr to find th minimum of th losss th cor library is xtndd by nw cor modls and nw thrmal modls for vry nw longatd cor gomtry. For ach winding width th sam basic arrangmnt was chosn. Th 14 turns of th primary sidd winding consist of solid wir, arrangd sid by sid in on layr. Th on turn scondary sidd winding consists of a coppr foil covrd clos to th primary winding. Thn th losss and th wight of th longatd transformrs wr calculatd using th rsults prsntd in [5] whil th cor losss wr accountd for by curv fitting with data from data books. Figur 14 shows th rsults obtaind. t can b sn, that a minimum of losss (at max. allowabl transformr tmpratur) will b in a rang of 50 mm up to 60 mm. 340

7 1 r ar prsntd. Th modling of a four winding transformr and of a rsonant inductor of a rsonant convrtr with trtiary sidd rsonant capacitor and th optimization of a transformr for a Two-Transistor-Forward-Convrtr. Th rsults obtaind ar in rmarkably good accordanc with th masurd quantitis. Rfrncs Figur 12: Circuitry of a th high dnsity Two-Transistor Forward Convrtr with 5V/200A output - cor + bobbin&ul(ilhl foil - \ cntr lg / Figur 13: Elongation of a E-30 cor in ordr to find minimum losss 5 Conclusion A nw CAD-program is prsntd, suitabl to dsign and optimiz switchd mod powr supplis containing high frquncy multiwinding transformrs and inductors. Aftr illustrating th structur of th CAD-program th dsign and modling procdur of high frquncy transformrs is shown in dtail. Sinc th quation implmntd in th CAD-program bas on a fild- and ntworkthortical analysis, th skin ffct can b considrd during th diffrnt dsign phass lading to a mor ralistical rprsntation of th physical situation. n this papr two xampls [l] R.B. Ridly, F.C. L, Practical Nonlinar Dsign Optimization Tool for Powr Convrir Componnts, PESC 1987, pp [2] T. Katan t al., Optimum Cor Dimnsions of 7"sformr for Switching Powr Supplis, PESC 1984, pp [3] P.M. Gradzki, M. Jovanovic, F.C. L, Compuir- Aidd Dsign of Hiqh-Frquncy Powr Transformrs, APEC 1990, pp [4] L. Hinmann, Modling of Multiwinding Transformrs at quasi-stationary Fild Distributions, Dissrtation (in Grman), Univrsity of Padrborn, 1993 [5] L. Hinmann, R. Ullrich, H. Grotstolln, Transfr Function and Calculation of Paramtrs for Hagh Frquncy Multiwinding Transformrs, PESC 1991, pp [6] L. Hinmann, R. Ullrich, B. Bckr, H. Grotstolln, Stat Spac Modling of High Frquncy Multiwinding Transformrs, PESC 1993, pp [7] L. Hinmann, P. Wallmir, R. Schulz, H. Grotstolln, Modling of High Frquncy nductors, PESC 1994, pp [8] L. Hinmann, N. Frohlk, H. Grotstolln, High Powr, High Frquncy Quasi-Zro- Voltag-Switchd PWM Forward Convrtr with vry low Ractiv Powr, Conf. Proc. of HFPC'93, pp [9] N. Frohlk, Switchd mod powr supply topologis and switching concpts for hiqh powr and low output voltag, Doctoral Thsis (in Grman), Univrsity of Padrborn, 1991 [lo] H.P. Ludk, Untrsuchvng von Schaltntrtiln mit Eontinuirlichn Rsonanrschwingungn, Doctoral Thsis, Univrsity of Padrborn, : &- mm Figur 14: Optimization of a transformr by variing th winding width 341