I. INTRODUCTION. Figure 1, The Input Display II. DESIGN PROCEDURE

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1 Ballast Dsign Softwar Ptr Grn, Snior ighting Systms Enginr, Intrnational Rctifir, ighting Group, 101S Spulvda Boulvard, El Sgundo, CA, as prsntd at PCIM Europ 0 Abstract: W hav dvlopd a Windows basd application to assist nginrs in th dsign of dimming or non-dimming lctronic ballasts for Fluorscnt lamps basd around th I.R. rang of lighting control ICs. Th softwar rducs th dsign tim dramatically by prforming th complx itrativ procdur rquird to optimiz th oprating points and componnt valus of th circuit. It producs a schmatic, a bill of matrials (listing all componnt valus) and winding spcifications for th inductors. Th softwar contains a databas of oprating paramtrs for 36 diffrnt typs of lamp with th ability to add nw lamps if rquird. It also supports 7 diffrnt configurations for on or two lamp ballast configurations. W hav also includd an inductor dsignr that will gnrat th spcifications for th rsonant output inductor as wll as th powr factor corrction inductor if usd. This procss is also itrativ and complicatd. Th softwar taks into account th vry high inductor currnt that occurs during lamp ignition. This avoids th possibility of ballasts shutting down at lamp ignition du to saturation of th output inductor. It producs dtaild spcifications that contain all th information that a winding company would nd in ordr to manufactur corrctly dsignd parts that will work in th ballast without problms. I. INTRDUCTIN Th ballast dsign softwar (to b rfrrd to as BD in this papr) is uniqu in th way that it simplifis th dsign procss to 5 simpl stps rquiring th usr to spcify only: 1. in Input oltag (US or Europ powr factor corrctd or non-powr factor corrctd). amp Typ (databas of 36 lamps with th ability for th usr to add additional lamp typs) 3. Control I.C. (rsion supports th IR156, th IR1571 and th IR159, rsion 3 will also support th IR166 and IR167) 4. Th output configuration (on or two lamps, dual lamp sris or paralll arrangmnt voltag or currnt mod cathod hating) Having don this th usr only has to prss th Dsign Ballast button and th softwar will produc a complt dsign that will work corrctly. Th dsign procss involvs som lngthy and complx calculations that nd to tak into account many diffrnt oprating paramtrs. Sinc it is an itrativ procss ths calculations must b carrid out svral tims in ordr to convrg and provid accptabl oprating points. ur softwar carris out this task almost instantanously saving th ballast dsignr many hours of tdious calculation and possibl rror. Figur 1, Th Input Display II. DESIGN PRCEDURE Th following paramtrs nd to b known in ordr to calculat th oprating paramtrs for a ballast nondimming dsign: (Th valus givn hr ar for a T8/36W lamp) Prhat Currnt: 0.6 [A] Prhat Tim: [sc] Max Prhat oltag: 600 [pp] Ignition oltag: 1500 [pp] Running amp Powr: 34 [W] Running amp oltag: 141 [pk] This information is containd within th lamp databas within th softwar. 1

2 In a dimmabl dsign ths additional paramtrs ar also ndd: amp : 1 [W] amp : 15 [pk] Min. Cathod Hating Currnt: 0.35 [A] (Th minimum powr is rquird whatvr minimum light output is rquird) Th BD softwar uss a simplifid modl to dsign th output stag. Magnitud Run Frquncy Ignition Prhat High-Q ow-q Figur 3, Transfr function of RC circuit with typical oprating points. in R C From this basic modl w hav xtrapolatd formula to calculat th prhat frquncy and voltag: f I [Hz] (1) π C Figur, utput stag simplifid modl A high prformanc ballast should provid th lamp with prhat currnt in th cathods for a spcifid tim to bring thm to th corrct tmpratur bfor ignition. During th prhat tim th lamp voltag has to b low nough to nsur that ignition will not occur prmaturly. At th nd of prhat a high voltag is rquird to ignit th lamp and from thn on th rquird currnt should b supplid to th lamp for opration at th corrct powr. Ths rquirmnts ar satisfid by changing th frquncy of th input voltag and proprly slcting; in, and C. For prhat and ignition, th lamp is not conducting and th circuit is rducd to a sris -C. During running, th lamp is conducting and th circuit is an in sris with a paralll R-C. Th BD uss th transfr functions for ach mod of opration in an itrativ procss to dtrmin th optimum valus for and C and to calculat th oprating frquncis. It is ssntial to choos th bst possibl and C valus to optimiz th dsign of th ballast. in in + + π π C whr, I () in Input squar-wav pak to pak voltag [olts] amp prhat pak-to-pak voltag [olts] I Filamnt prhat RMS currnt [Amps] utput stag inductor [Hnris] C utput stag capacitor [Farads] Ths quations tak account only of th fundamntal frquncy of th squar wav producd by th half bridg switchs. Harmonics that xist at highr frquncis ar assumd to hav a ngligibl ffct. Exprimntal rsults hav confirmd that this assumption dos not produc inaccurat rsults. Th abov formula ar usd to dtrmin th prhat rquirmnts in a ballast that usd currnt mod prhating which is th simplst approach. Som lamps rquir additional windings from th inductor or an additional transformr to provid th cathod hating bcaus it is not possibl to provid th corrct currnt using valus of and C that ar suitabl for th running rquirmnts of th lamp. Th BD softwar uss a diffrnt mthod of approximation if such a configuration is slctd. A configuration that rlis on auxiliary windings from th inductor to

3 provid th prhat is trmd voltag mod. This trm dos not imply that such a mthod would provid a constant voltag at th cathods. During ignition th frquncy for a givn ignition voltag is calculatd using (3), sinc th lamp is still an opn circuit. Whn calculating th dsign paramtrs for a dimming ballast th BD softwar also utilizs th quation usd to dtrmin th running frquncy at maximum output, to dtrmin th oprating frquncy at minimum output. Th lamp databas contains th masurd lamp voltag and powr for ach lamp typ at light output. fign 1 π 4 in 1+ π ign C [Hz] (3) [Hz] (7) An additional quation is usd to calculat th cathod hating currnt at minimum output, whr, ign amp ignition pak to pak voltag [olts] Th associatd ignition currnt amplitud flowing in th circuit that dtrmins th maximum currnt ratings for th inductor and th half bridg MSFETs, bcoms: Iign figncign π (4) Th softwar uss this currnt to dsign an inductor that will not saturat during ignition. This is important sinc othrwis th ballast would shut down at ignition. nc th lamp has ignitd th R in th modl must b includd in th quation so th following formula is usd for calculating th running frquncy: 4 in f run π run + C R C π C R C C [Hz] (5) whr R has bn assumd to b th linarizd lamp rsistanc dtrmind from th lamp running powr and voltag at a singl oprating point: run R P run whr, P run run [hms] (6) amp running powr [Watts] amp pak running voltag [olts] f 1 π 1 3P C C P C C 4 Using th abov sris of quations, th softwar is carry out calculations vry rapidly and dtrmin I Cath f πc whthr an accptabl rsult is obtaind. If not it will itrat th valus of and C until corrct rsults ar achivd. Naturally th valus of rsistors and capacitors usd for programming th frquncis and othr oprating paramtrs for th ballast control IC ar calculatd dirctly using th formula that hav bn publishd in th data shts for ach part. Ths ar dirctly calculatd from th frquncis that th softwar has dtrmind ar corrct for th and C slctd and th oprating paramtrs of th systm. III. Simpl pration 4in 1 π C Whn th BD softwar in simpl mod, th usr will nvr s any paramtrs or calculatd rsults. At th nd only a schmatic with a bill of matrials and spcifications for th output inductor and powr factor corrction inductor ar producd. This allows usrs to obtain th information ndd to construct a ballast without bing involvd in or nding to undrstand th complx procss of dsign. I. Advancd pration (8) Th BD softwar also has advancd options that allow th dsignr to adjust th paramtrs or fix th valus 3

4 of th output inductor and capacitor. Having don this th softwar will thn rcalculat th oprating points and componnt valus rquird basd around ths valus. Th usr will s a graical display showing th prhat, ignition and running frquncis (for dimming dsigns th maximum and minimum frquncis ar givn) of th systm and thy will b abl to s if ths ar accptabl. Th calculatd paramtrs can also b displayd and th usr is abl to adjust thm and thn rcalculat should thy wish to xprimnt with possibl valus of and C othr than thos providd by th softwar. It is also possibl to adjust th othr oprating paramtrs to find out what th ffct would b if somthing wr to b altrd. PFC ( f MIN P I pk MAX). Whr, P ) (9) ( (10) RMS lin voltag input utput DC bus voltag f Minimum PFC switching frquncy P MIN utput Powr I. Inductor Dsignr Th BD softwar also includs a complt inductor dsign fatur that producs spcifications for th ballast output inductor and PFC inductor (if applicabl). Th spcification provids all of th following information from which an inductor can b manufacturd that, if wound corrctly, will b vry clos in valu to th rquird valu and will b accptabl for building into th ballast prototyp circuit: Figur 4, Advancd Display. Powr Factor Corrction Th BD softwar will also calculat th valu of th inductor usd in a dsign that mploys an activ powr factor corrction front nd basd on a critical conduction mod boost rgulator. Th currnt vrsion of th softwar () supports only th IR156, IR1571 and IR159, which do not hav built in powr factor control. Thy spcify an industry standard controllr in th bill of matrials and show this in th schmatic. Th nw ICs th IR166 and IR167 ar quivalnt to th IR156 and IR1571 plus built in powr factor control utilizing a simplifid control mthod that ngats th rquirmnt for using an additional control IC. (Ths nw ICs will b fully supportd in rsion 3 of th BD softwar, currntly undr dvlopmnt.) In ithr cas, sinc critical conduction mod is usd, th quation to dtrmin th inductanc rquird and th pak currnt will b xactly th sam. Cor Siz Gap ngth Winding wir diamtr Numbr of turns Th softwar contains a databas of cor paramtrs for standard E cors mad of standard powr grad Frrit matrial. Th facility has also bn includd for th usr to add additional cor spcifications to th databas allowing any cor to b dsignd into th systm. Th cor data is stord in a Microsoft Accss databas. It should b notd that th cor databas should contain cor information in ascnding ordr of cor siz in ordr for th softwar to function corrctly. This is bcaus th dsign procss bgins with th smallst siz and calculats until it rachs a siz whr th rquird inductanc and pak currnt can b ralizd without th cor saturating, i.. xcding a spcifid limit of flux dnsity. Th limit of 300mT has bn chosn bcaus this is vry consrvativ and should provid nough hadroom so that whn th cor tmpratur is high th inductor will nvr saturat undr worst-cas conditions of pak currnt. 4

5 Th softwar also calculats th rquird wir diamtr for th lamp running currnt and thn works out whthr th numbr of turns can b supportd on th bobbin siz availabl that will provid th corrct inductanc for th gap spcifid. Th procss bgins with a small gap and calculats th numbr of turns thn th pak flux dnsity during ignition or worstcas pak currnt for a PFC inductor. If th flux dnsity is too high a largr gap will b trid until a siz of gap is found that will produc accptabl rsults. If no accptabl combination can b found th nxt siz up of cor will b trid, starting with a small gap and th procss will tak plac again until th bst solution is found. In this way th softwar savs th dsignr a considrabl amount of tim bcaus this procss actually carris out th calculations for many combinations until th optimum on is discovrd. Th softwar producs an inductor spcification that can b printd out and snt dirctly to a coil windr. As in advancd mod of th ballast dsign part of th softwar, th inductor will allow th cor siz or gap siz or both to b fixd. If th cor siz is fixd thn th softwar will calculat th gap siz that will produc th bst rsult and display th pak flux dnsity, giving a warning if it is abov 300mT. Th sam will happn if th gap siz is fixd, th minimum siz of cor that may b usd with this gap will b output. In th cas of both cor and gap bing fixd th softwar will simply calculat th numbr of turns and th pak flux dnsity undr worst-cas conditions of pak currnt. Th numbr of turns rquird for an inductor with a spcific cor siz and gap is giv by: N (11) A Th Al valu can b calculatd from: A µ µ 10 6 ( l / A) (nh) (1) Whr µ varis dpnding on th siz of th gap and b calculatd from: µ i µ G µ i 1+ l (13) Th pak flux dnsity is givn by: B MAX N A I A MAX (14) Summary Figur 5, Inductor spcification Th lighting group at I.R. has dvlopd a uniqu and xtrmly usful dsign tool aimd at assisting our customrs and rducing th dvlopmnt tim rquird. It has bn fully tstd and has producd xcllnt rsults with ballast circuits that function without many of th common problms xprincd by dsignrs. It savs tim and tdious rptitiv work on th part of nginrs and rducs th possibility of 5

6 rror allowing th customr to cut down on dvlopmnt tim of thir first prototyp allowing thm to gt somthing working on th bnch mor quickly. This softwar can b downloadd from th Intrnational Rctifir wbsit at It is asy install and us on a P.C. rsion 3, which incorporats additional control ICs and faturs is currntly undr dvlopmnt. REFERENCES [1] Intrnational Rctifir Thomas J. Ribarich, John J. Ribarich A Nw Procdur for High-Frquncy Elctronic Ballast Dsign [] Intrnational Rctifir Thomas J. Ribarich Elctronic Ballast Dsign Part 1 : IR1571 Part : IR159 [3] Intrnational Rctifir Ptr Grn Procdur for dsigning Ballast utput Inductor 6