IEEE ICSS5 Inernaional Conference On Syem & Signal A New Power-Facor-Correcion Circui wih Reonan Energy Tank for Cla D Inverer Ying-Chun Chuang Deparmen of Elecrical Engineering, Kun Shan Univeriy of Technology Tainan Hien, Taiwan, R.O.C. Tel:886-6-559 Fax:886-6-598 E-mail:chuang@mail.ku.edu.w Hung-Shiang Chuang Deparmen of Auomaion Engineering Kao Yuan Iniue of Technology Kaohiung, Taiwan, R.O.C. Tel:886-7-6778 Fax:886-7-677 E-mail:chuangh@cc.kyi.edu.w Abrac A new filering echnique named reonan energy orage filer for AC/DC converer i propoed in hi paper. A compared wih he convenional acive filer, hi approach i advanageou of lower curren re and higher conrol flexibiliy. In hi paper, he propoed filering approach i implemened wih cla-d erie-parallel reonan inverer. The experimenal reul are provided o validae he heoreical analye. I i proven ha he propoed approach can achieve nearly uniy power facor and very low harmonic diorion. I. INTRODUCTION Power elecronic circui wih high-frequency cla-d reonan inverer are broadly ued in many equipmen uch a elecronic balla, wiching power upplie, baery charger, and o on. Convenionally, hee equipmen, when exracing power from he ac line ource, ofen ue a diode recifier bridge wih a bulk elecrolyic capacior o provide mooh dc-link volage for he high-frequency cla-d inverer. Such a recifier circui ineviably draw an inpu curren of narrow pule, which i nooriouly of very poor power facor and eriou harmonic conen. Hence, a low co and imple rucure filer circui become required in he deign of he dc-linked cla-d inverer. Among many filering opologie, he power-facor-correcion (PFC) echnique wih a boo converer ha been proven o be efficien and imple [-]. Thi approach, however, i a he expene of an addiional power converer wih ophiicaed conrol leading o high co and lower overall efficiency. In an aemp o earch for a more compac, efficien and co-effecive oluion, many deign wih ingle-age converer have been developed [-7]. All hee approache make an inegraion of wo power converer, he power facor correcion age and he cla-d inverer. In hi inegraed circui, he energy proceing cheme i he ame a ha of he wo-age PFC circui. An inducor wih addiional power emiconducor device i needed for emporarily oring he energy upplied from he ac line ource, and hen ranferring he energy o he dc-link capacior. The average of he high-frequency wiching curren i made o follow he inpu line volage o achieve a high power facor. In order o reduce wiching loe, he inducor curren can deliberaely be operaed a diconinuou conducion mode (DCM)[]. Hence wichingon loe can be eliminaed. However, hi converer will be wiched off a i peak curren during every wiching cycle reuling in coniderable loe. To improve hi drawback, hi paper preen a new PFC circui wih a reonan energy ank by which boh wiching-on and wiching-off loe can be relieved. The propoed approach can eaily be inegraed ino he cla-d inverer age a a ingle-age high-power-facor inverer. An implemenaion on he erie-parallel reonan inverer i illuraed a a deign example. II. CIRCUIT CONFIGURATION AND ANALYSIS A. Circui Configuraion Fig. how he baic configuraion of he propoed PFC circui. Inead of he inducor ued in he convenional PFC circui, an energy reonan ank compriing an inducor and a capacior i ued a he elemen for emporary energy orage. The energy ank draw curren from he ac line during he wiching-on of he acive wich, S, in every high-frequency wiching cycle. When S i wiched off, he energy ored in he energy ank i ranferred o he dc-link capacior, C, hrough he energy ranfer diode, Dpf. C i a bulk elecrolyic capacior o provide a mooh dc-link volage for he cla D inverer age. Since S i wiched on and off a a high frequency, he inpu curren become a pulaing waveform a he ame frequency. By properly conrolling he ampliude and duraion of he pulaing curren, he average of he inpu curren can be made o be inuoidal and in phae wih he inpu volage. The high frequency conen in he inpu curren can imply be removed by a mall filer a he inpu erminal. Conequenly, a nearly uniy power facor and very low harmonic diorion can be achieved. v () - i() _ i Lpf Lpf i Cpf Dpf Cpf - vcpf S d Conrol Circui C v dc _ Cla D Inverer Sage Fig. PFC Circui wih reonan energy ank A compared wih he PFC circui a a boo inducor, he peak of he reonan curren i maller han he boo a
IEEE ICSS5 Inernaional Conference On Syem & Signal hown in Fig.. Moreover, he power wich can be deliberaely wiched off a a much maller curren, ideally a he zero curren. Thi mean ha he wiching off lo can be reduced or even eliminaed. i Reonan Curren Ih Ip Inducor Curren I Lpf,ave /o T Fig. Comparion of reonan curren and inducor curren B. Circui Operaion and Analyi Auming he PFC circui i upplied from he ac line volage ource. v Vm in () where Vm i he peak volage and i he line frequency. In order o urn on he power wich a zero curren, he PFC circui i deigned o operae a DCM. In addiion, he dc-link volage mu be higher han he peak value of line ource volage. When he power wich S i urned on, he recified line ource volage i applied on he reonan energy ank and a reonan curren i drawn from he ac line ource. The inducor curren waveform i hown in Fig.. ilpf C pf v ino L () pf whereo i he reonan frequency of he reonan energy ank and o/ L pf C pf The reonan frequencyo i deigned o be much higher han line frequency, herefore, inpu volage can be conidered a conan during a reonan cycle. d i L.6.4. o I LO d Mode I Mode II Mode III Mode I Fig. Curren waveform of reonan energy converer Wheno, S i wiched off, he energy diode Dpf urn on and he energy ored in he inducor i delivered o T he dc-link capacior. During hi period, he inducor curren decreae linearly. ilpf V V dc ( ) I LO L pf o where I Lo i he iniial curren in he inducor. Meanwhile, he energy ored in he capacior of he reonan ank i releaed o he following age. The ime d needed for he inducor curren i Lpf o decline o zero can be calculaed by ubiuing () ino (). V d LC in (4) VdcV The average inducor curren I Lpf,avg in a wiching cycle can be obained a follow C pf I I o LO d Lpf, avg ( V ino ) d T L pf T C pf V V co in (5) T VdcV The effecive curren can be calculaed a: C T V VdcV L, ( ) co in Lpf rm V d (6) where i he angle of he line volage. The average inpu AC power i Pin VI Lpf, aved C pf V V co in d T VdcV The inpu power facor can be calculaed a Pin PF VI Lpf, rm V, rm (7) C pf V V co in d T VdcV (8) Cpf V V co in d T VdcV where V, rmvm/ i he effecive value of he inpu volage. The raio of he peak value of he inpu volage o he dc-link volage i denoed by. Vm (9) Vdc ()
IEEE ICSS5 Inernaional Conference On Syem & Signal Subiuing (9) ino (8), he power facor can be rewrien a: in co in d in PF () in co For impliciy, () can be expreed a: x PF y in in in d in The wo complex erm, x and y, in he equaion are: x in in co in d in co in { [ an ( )]} in y in co in d in co co in { [ an ( )]} 4 4 in { 4 ( ) 4 [ an ( )]} () () () Equaion () indicae ha he power facor i a funcion ofanda hown in Fig. 4. Generally, he power facor increae a volage raioincreae, expec whenbecome cloe o.. Beide, a beer power facor can be acquired for a large. Ifi greaer han 4π/5, no maer wha volage raio i, uniy power facor can be achieved. PF.9.8.7.6.5 =.8 =.9 =.7 =.6 =.5 =.4 5 5 5 4 5 Fig. 4 Calculaed power facor III. IMPLEMENTATION ON CLASS-D RESONANT INVERTER The propoed approach i implemened on a cla-d erie-parallel reonan inverer a hown in Fig.. 5. The circui encloed by dah line denoe he propoed filer circui. I coni of a pair of reonan energy ank and a pair of energy ranfer diode. The wo reonan energy ank commonly ue he ame inducor, L, and he acive wiche employ he exien power wiche of he inverer. - v() Dr Dr4 i() L i L () vcx() - Dr Dr vcy() - Dx icx() Cx Vdc - icy() Cy Dy Q C Q L io() D D C C L Cla-D erie-parallel reonan inverer Fig. 5 Cla-D erie-parallel reonan inverer wih he propoed PFC circui A he low volage of recified line ource, he circui i operaed a diconinuou curren mode a hown in Fig. 6. The peak value of capacior volage v cx i le han V dc and he inducor curren, i L, i mall and will reonae o zero. The operaion can be divided ino 5 ime inerval. During inerval I, he ranior, Q, i urned on and carrie boh i o and i L. The capacior, C x, i charged by hi inducor curren and v cy i clamped a zero. A he end of hi inerval, he inducor curren reonan o zero, v cx reache i maximum. A hi inan he recifier and he diode D y are revere-biaed. During inerval II, he load curren flow hrough Q and i L ay a zero. A he beginning of inerval III, Q i wiched off, and he energy ored in C x i ranferred o he load and v cx decline. When he recified line volage become greaer han v cx, he recifier diode become forward biaed and inerval IV begin. Meanwhile, he line ource ar o charge C x and C y hrough he inducor. However, hi charging curren i le han i o which dicharge C x. Therefore, v cx coninuouly decreae and fall o zero evenually. The diode D urn on a he beginning of inerval V, and carrie he freewheeling curren which i equal o he difference beween i L and i o. A he end of inerval V, he freewheeling curren come o zero and he ranior, Q, i wiched on. Since he wiche are operaed ymmerically and C y i equal o C x, he operaion of he nex half cycle i imilar. A he high volage of he recified line ource, he inducor circui i coninuou and of very mall ripple a hown in Fig. 7. The operaion can be divided ino 4 ime inerval. Inerval I ar a he inan when Q i wiched on. Prior o hi ime, C x ha been charged up and clamped a V dc. Since C i very large a compared wih C x, mo of he inducor curren flow hrough C via D x, herefore, Q carrie only he
IEEE ICSS5 Inernaional Conference On Syem & Signal.8.4 -.4 -.8 i o i L.8.4 -.4 -.8 io il.8.4 vcx i Q v cy.8.4 v cx i Q v cy.8.8.4 i D I II V III IV Fig. 6 Theoreical waveform for diconinuou curren mode load curren. A he beginning of inerval II, Q i wiched off and he energy ored in C x i ranferred o he load. Meanwhile, C y ar o be charged by he inducor curren. Alhough v cx declined, he volage of C y increae rapidly becaue he inducor curren i high, herefore he um of v x and vy may reach V dc, hen he diode D y become forward biaed. A he inducor curren moly flow hrough C during inerval III, C x i coninuouly dicharged by i o. When C x i compleely dicharged, D urn on and carrie he freewheeling curren. A he momen when he freewheeling curren come o zero, Q i wiched on and he nex half cycle enue. Fig. 8 how he calculaed inpu curren waveform over half a cycle of he line ource. In hi figure, he inverer frequency i made low and he line-frequency conen are no filered for he purpoed of illuraion. I can be found ha A.4... i L () / Fig. 8 Calculaed inpu curren waveform..4 i D I II III IV Fig. 7 Theoreical waveform for coninuou curren mode he inpu curren i diconinuou over he lower range of he ac-line volage while becoming coninuou over he higher volage range. The pulaing curren diher around a inuoidal fundamenal wave, which i in phae wih he inpu volage. Removing he line-frequency conen, a nearly inuoidal inpu curren can be obained. IV. DESIGN CONSIDERATIONS In order o achieve uniy power facor, he average inducor curren hould be made o follow i fundamenal wave which i in phae wih inpu line volage. The fundamenal curren can be deermined by he inpu power and he volage pecificaion. Then, he opimum capaciance can be calculaed Pin Cx (4) 4 fv where P in and V denoe he pecified inpu power and volage, repecively and f i he wiching frequency of he cla D reonan inverer. The opimum capaciance i choen o uain he power facor cloe o uniy. Then he wich-off angle can be deermined accordingly. However, i hould be reminded ha he high-frequency capacior can no be oo large ince hey ha o be compleely deenergized before he ranior on he ame ide ha been urned on. Oherwie, he reidual charge would be hor circuied a he wiching on of he ranior. Thi bring abou a curren pike ha may damage he circui componen.
IEEE ICSS5 Inernaional Conference On Syem & Signal Since he maximum volage of he high-frequency capacior i limied o he dc-link volage, he maximum energy ored in he capacior i Ec(max) C xvdc (5) The capacior energy begin o dicharge a he inan of wiching off he oppoie ranior. The dicharging rae i proporional o he difference beween he load curren and he boo inducor curren. The load curren i wih conan ampliude while he average curren of he boo inducor ubanially follow he inpu line volage. Thi implie ha he lowe dicharging rae happen a he peak of he inpu line curren. In pracice, a illuraed in Fig. 7, he boo inducor curren around he peak poin i wih a very mall ripple o ha can be aumed o be a conan. Fig. 9 illurae ha he available dicharging inerval i approximaely fromo-. Wihin hi inerval, he load curren ha rien up and become greaer han he inducor curren. In oher word, he ranior can only be urned off afer, bu hould be urned on before-. Thi figure reveal ha he circui can work properly only when he ampliude of he load curren i greaer han ha of he inpu curren. For he pecified inpu power and he load curren, he maximum capaciance can be calculaed L (7) o C x On he oher hand, he wiching-off angle may be predeermined in ome pracical deign. In hi cae, he deign procedure can be curried ou inverely. V. EXPERIMENT RESULTS A cla D reonan inverer wih PFC circui of Fig. 5 i deigned and buil o drive a fluorecen lamp of 6W. The circui parameer are lied in Table. Fig. and how he meaured experimenal waveform of he laboraory circui, and hey are quie conien wih hoe imulaed. Fig. how he meaured inpu line volage and curren. Thi new deign can achieved a high power facor greaer han.99 and a low oal harmonic diorion le han 8%. The overall operaing efficiency can be greaer han 9%. Table Circui parameer Inpu volage V V, 6Hz Swiching frequency f 8kHz Dc-link volage V dc V Capacior C x, C y 4.7nF Inducor L.5mH Pi C x(max) I m co (6) o VdcV m The eleced capaciance i rericed by hi maximum value if i i le han he opimum capaciance calculaed from (4). Under hi condiion, he power facor would be deerioraed. A v cx () i L ().6.4. i o () i L (peak) Time: 5u/div Volage: v/div Curren:.A/div (a) v cx () i L () Fig. 9 Relaionhip beween i o () and i L () a=/. A decribed above, he boo inducor alo erve a a curren moohing reacor. A larger inducor can make a maller ripple in he inpu curren. However, he inducance hould be mall enough o a o enure ha he half-cycle reonance can be compleed and he capacior volage can be charged o i maximum value before he oppoie ranior ha been wiched off. Therefore, once he capaciance and he wiching-off angle are given, he inducance can hen be obained Time: 5u/div Volage: v/div Curren:.A/div (b) Fig. Meaured waveform of inducor curren and capacior volage a (a)=/8 and (b)=/.
IEEE ICSS5 Inernaional Conference On Syem & Signal i o () i Q Time: 5u/div i io() Q Time: 5u/div i D Curren:.5A/div (a) i D Curren:.5A/div (b) Fig. Curren waveform of ranior, aniparallel diode, and load curren a (a)=/8 and (b)=/. v () i () Time: 5m/div Volage: v/div Curren:.A/div Fig. Experimenal waveform of inpu line volage and curren VI. CONCLUSIONS A new PFC circui wih reonan energy ank for cla D inverer ha been preened. Theoreical and experimenal reul prove ha almo uniy power facor can be achieved. Wih wo energy orage elemen, he conrol flexibiliy can be improved. When he acive power wiche are deigned o be ofly wiched on and off a zero curren, he wiching loe can be compleely eliminaed and leading o high efficiency. Moreover, he peak of he inducor curren i maller a compared wih he convenional PFC circui. Therefore, a maller inducor can be ued and he curren ree on he power wiche can be reduced. VII. REFERENCES [] K. H. Liu, and Y. L. Lin, "Curren Waveform Diorion in Power Facor Correcion Circui Employing Diconinuou-Mode Boo Converer," Conference Record of IEEE Power Elecronic Speciali Conference, pp. 85-89, 998. [] M. Kazerani, P. D. Zioga, and G. Joo, "A Novel Acive Curren Wavehaping Technique for Solid-Sae Inpu Power Facor Condiioner," IEEE Tran. on Ind. Elecron., Vol. 8, No., pp. 7-78, Feb. 99.. [] R. de Oliveira Briochi, and J. L. F. Vieira, "High-Power-Facor Elecronic Balla wih Conan DC-Link Volage," IEEE Tranacion on Power Elecronic, Vol., No. 6, pp. -7, Nov. 998. [4] C. Liciral, L. Maleani, G. Spiazzi, P. Teni, and A. -Ended Sof-Swiching Elecronic Balla Applicaion, Vol. 9, no., pp. 8-87, March/April 99. [5] E. Deng, and S. Cuk, "Single Sage, High Power Facor, Lamp Balla," Conference Record of IEEE Applied Power Elecronic Conference, pp. 44-449, 994. [6] C. Licira, L. Maleani, G. Spiazzi, P. Teni, and A. Tea, "Single-Ended Sof-Swiching Elecronic Balla wih Uniy Power Facor," IEEE Tranacion on Indury Applicaion, Vol. 9, No., pp. 8-87, March/April 99. [7] -Swiching Power Appl., Vol. 8, pp. 86-96, Non. 99.