Integrated Forward Half-Bridge Resonant Inverter as a High-Power-Factor Electronic Ballast

Transcription

1 Inegraed Forward Half-Bridge Resonan Inverer as a High-Power-Facor Elecronic Ballas Absrac.- A novel single-sage high-power-facor elecronic ballas obained from he inegraion of a forward dc-o-dc converer and a half-bridge resonan inverer is evaluaed in his paper. The Forward converer is operaed in disconinuous conducion mode and consan frequency providing an inpu power facor high enough o saisfy presen sandard requiremens. The operaion of he proposed ballas is also invesigaed in deail in his paper. A ballas prooype for a 36W fluorescen lamp has been boh simulaed and implemened a he laboraory. I. INTRDUCTIN Nowadays he use of elecronic ballass o supply discharge lamps is increasing, especially for fluorescen lamps due o he increase in he luminous efficacy a high frequency. For oupu power over 5W, elecronic ballas has o mee he IEC regulaion [1]. Presenly, an inensive work is being carried ou in order o obain low cos and high efficiency opologies o implemen elecronic ballass. In search of low cos and high power facor for elecronic ballass several reduced componen coun opologies has been previously proposed [3-8]. ne of he ways o reduce cos in high power facor elecronic ballass is he inegraion of wo sages, a dc-o-dc converer and a resonan inverer, in a single sage by sharing one or more swiches []. Figure 1 shows four of hese low-cos high-power-facor elecronic ballas obained from he inegraion of a simple dc-o-dc converer wih a half-bridge resonan inverer. In order o reduce cos he dc-o-dc converer is operaed in disconinuous conducion mode wih a simple conrol circui, which is also used o conrol he resonan inverer. Figure 1a shows a high-power-facor elecronic ballas obained from he inegraion of a boos dc-o-dc converer and a half-bridge resonan inverer [5]. In his converer a high inpu power facor is obained when he boos converer is operaed in dcm provided ha he oupu volage is high enough o avoid he non lineariies of he averaged inpu curren [5]. Normally he oupu volage has o be as high as wice he peak line volage, producing a considerably high volage sress across he swiches. Anoher imporan disadvanage of his ballas is he power source behavior of he boos converer when operaed in dcm and open loop, wha means a coninuously increasing volage across he bulk capacior when lamps are disconneced. Thus, in order o avoid ballas desrucion he implemenaion of an addiional overvolage proecion is mandaory for a safe ballas operaion wihou lamps. Figure 1b, 1c and 1d illusraes he elecric diagram of oher hree inegraed ballas using he flyback dc-o-dc converer (Fig. 1b), buck-boos dc-o-dc converer (Fig. 1c) and (Fig. 1d), Buck dc-o-dc converer. The characerisics of flyback and buck-boos ballass are very similar since hey come from he same basic opologies and he only difference is ha he flyback converer provides he urn raio of he coupled inducors as an exra parameer for design. The main advanage of hese ballass is ha flyback and buck-boos converers operaed in dcm behave as a resisance for he mains wihou any resricion in he oupu volage across he bulk capacior. Also, he volage across bulk capacior can be quie lower han ha for he boos inegraed ballas, hus requiring a cheaper and smaller capacior. However, in hese opologies he overvolage problem when operaed wih no load persiss, making necessary he use of some kind of proecion. In he buck opology he over-volage problem when operaed wih no load persis, making unnecessary he use of some kind of proecion. The aim of his paper is o evaluae a fifh possibiliy o implemen a high power facor elecronic ballas based on he inegraion of a forward dc-o-dc converer wih a half bridge resonan inverer. In his way, a very ineresing opology is obained, which can achieve high inpu power facor and saisfies he IEC Class C requiremens by operaing he forward converer in disconinuous conducion mode. Moreover, he proposed opology presens a naural proecion againsno load operaion wha makes i very ineresing o implemen low-cos high-power-facor elecronic ballas in he range of low-medium power. This paper is organized as follows. Secion II presens he proposed opology and is basic operaion and characerisics. Secion III presens he deailed operaion and he differen operaing modes. Secion IV illusraes a complee design example

2 for a commercial fluorescen lamp ballas wih a 36W lamp. Secion V presens some simulaion and experimenal resuls. Finally some conclusions are given o summarize he paper. II. PRPSED BALLAST AND BASIC CHARTERISTICS Figure illusraes he derivaion of he proposed opology from he forward dc-o-dc converer and he half-bridge resonan inverer. As shown in Fig. a, he wo swiches, Q0 of he buck converer and of he resonan inverer, can be inegraed in a single swich, which can be driven from he same conrol circui as ha for he resonan inverer. Figure b shows he final opology wih he wo swiches inegraed in a single one consiued by semiconducors,, and. The power facor characerisics of he Forward dc-o-dc converer operaing in disconinuous conducion mode is similar in several ballas, inpu curren shaper based elecronic ballas In order o use his converer as a preregulaor for he proposed ballas he operaion of his converer as a high inpu power facor sage will be reviewed here. Figure 3 illusraes he inpu waveforms a high and low frequency for he DCM operaion of he Forward converer. The mean inpu curren of he forward converer can be expressed as follows: i g med () = 1 ( nv () V ) n D Ts g L (1) However, when operaed as power facor correcion sage he forward converer will only allow he inpu curren o circulae when inpu volage nv g is higher han oupu volage V 0, hus he averaged inpu curren can be beer expressed in he following way: ig() = 1 ( nv () V ) n D T if nvg V0 g 0 L s if nv () < V g () Figure 3b illusraes he inpu curren waveform of he forward converer a line frequency. This inpu waveform is exacly he same as ha obained for he high-power-facor elecronic ballas based on he inpu curren shaper presened in [10] and he buck ballas in he reference [11].. Figure 4 shows he power facor and oal harmonic disorion for an inpu curren waveform as ha shown in Fig. 3. In order o saisfy he IEC requiremens a minimum conducion angle θ of 130 degrees is necessary. A his operaion poin a power facor of 0.96 and a oal harmonic disorion of 9 percen are obained. The inducor curren of he forward converer a high frequency is shown in Fig. 3a. The mean inpu curren can be calculaed as follows: πθ = 1 π θ π vg () vg () 1 i Lmean () sen w L sen w L dw L (3) R S V n This curren is injeced ino he oupu ne of he buck converer bu only during he conducion inerval given by θ. The dc componen of (3) goes hrough he load resisance of he converer, hen he relaionship beween he peak line volage (V g ) and he oupu volage (V 0 ) is obained as follows: V () (4) = v g () V v () g 1 arcsen R S πv vg () π πr S V 1 vg () 1 Ri n where R i represens he equivalen inpu resisance of he resonan inverer semi-sage, and depends on he resonan ank elemens and swiching frequency, n is he relaion ship of he ransformer. III. DETAILED PERATIN Figure 5 illusraes he differen operaing modes of he proposed ballas and Fig. 6 shows he operaing waveforms a high frequency for a general operaion poin wih nv g <V 0. As can be seen in his figure six opologic modes appear for he operaion of he proposed ballas. Transisor ogeher wih diodes, and handle boh forward converer and resonan inverer currens, whereas ransisor and diode only handle he resonan

3 curren of he inverer. For he forward semi-sage, he operaion is assumed o be a consan duy cycle and frequency and in DCM, in order o have and average inpu curren proporional o he inpu volage. For he halfbridge semi-sage he operaion is assumed above resonan frequency, in order o aain ZVS commuaions for ransisor. In a normal half-bridge resonan inverer he operaion above resonance gives ZVS commuaions for boh swiches. In his case, for he single-sage high-power-facor ballas, ZVS commuaions are obained for whereas presens ZCS commuaions.. The analysis of he resonan inverer and ballas design mehodology will be included in he full version of his paper. IV. DESIGN EXAMPLE AND EXPERIMENTAESULTS A prooype of a ballas for wo linear fluorescen lamps has been designed, simulaed and implemened a he laboraory. The inpu volage is 30 Vrms-50Hz, and he lamp used is linear fluorescen lamp L-36W from sram. The following values have been obained: Buck semi-sage: D=0.41 U 0 =8 P o =36W L0=3.3 mh, C0=49uF Inverer semi-sage: f R = 50 khz, Z B = MP = 1 hm. = 0.67 mh, = 15 nf, ϕ E = 45 º (resonan curren phase angle) The seleced swiching frequency was 50 khz. Swiches are MSFET IRF840 from Inernaional Recifier and diodes are BA157. Figure 7 shows he elecrical diagram of he simulaed and implemened prooype. Some simulaed resuls will be included in he full version of his paper. Figure 8 shows he inpu waveforms measured a he laboraory, he conducion angle of he main recifier diodes is 130 degrees and sandard IEC class C requiremens are fulfilled. Figure 9 illusraes he curren waveform hrough ransisor, carrying boh forward and resonan inverer curren, and he volage Uds. Finally, fig. 10 shows lamp waveforms, sinusoidal waveforms wih low curren cres facor are obained. Measured efficiency was 85%. More deailed resul regarding harmonic conens of he inpu curren compared wih sandard requiremens will be presened in he full version of his paper. V. CNCLUSINS A new single-sage high-power-facor elecronic ballas has been presened in his paper. The ballas is obained from he inegraion of a forward dc-o-dc converer sage and a half-bridge resonan inverer. The buck converer is operaed in disconinuous conducion mode and consan frequency providing an inpu power facor high enough o saisfy presen sandard requiremens. The operaion of he proposed ballas is also invesigaed in deail in his paper. A ballas prooype has been also simulaed and implemened a he laboraory o evaluae is possibiliies. REFERENCES [1] IEC ( ) sandards on elecromagneic compaibiliy (EMC), Par 3, Secion : Limis for harmonic curren emissions. Inernaional Elecroechnical Commission, Geneva, Swizerland, April [] M. Madigan, R. Erickson, E. Ismail; "Inegraed High Qualiy Recifier-regulaors", IEEE PESC'9 proceedings, pp , 199. [3] E. Deng, S. Cuk; "Single Sage, High Power Facor, Lamp Ballas", IEEE APEC'94 proceedings, pp , [4] R.N. Prado, S. A. Bonaldo, M.C. Moreira, D.L.R. Vidor; "Elecronic Ballas wih a High Power Facor for Fluorescen Lamps", IEEE PESC'96 proceedings, pp , [5] C. Blanco, J.M. Alonso, E. López, A.J. Calleja, M. Rico; "A Single-Sage Fluorescen Lamp Ballas wih High Power Facor", IEEE APEC'96 proceedings, pp [6] J. M. Alonso, A. J. Calleja, E. López, J. Ribas, F. J. Ferrero and M. Rico; Analysis and experimenal resuls of a single-sage high-power-facor elecronic ballas based on flyback converer, IEEE APEC'98 proceedings, pp [7] J. M. Alonso, A. J. Calleja, F. Ferrero, E. López, J. Ribas and M. Rico-Secades; "Single-sage consan-waage high-power-facor elecronic ballas wih dimming capabiliy", IEEE PESC'98, pp , Fukuoka, Japan, [8] T.F. Wu and T.H. Yu; "ff-line applicaions wih single-sage converers," IEEE Tran. on Indusrial Elecronics, vol. 44, no. 5, pp , ocober [9] H. Endo, T. Yamashia and T. Sugiura; "A high-power-facor buck converer," IEEE PESC conf. record, pp , 199.

4 [10] M.C. Ghanem, K. A. Haddad and G. Roy; "Uniy power facor scheme using cascade converers," IEEE IECN conf. proc., pp , [11] J. M. Alonso, A. J. Calleja, J. Ribas, E. López, M. Rico, J. Sebasián; "Using Inpu Curren Shaper in he Implemenaion of High-Power-Facor Elecronic Ballass," IEEE APEC'99, pp , Dallas, [1] J. M. Alonso, A. J. Calleja, J. Ribas, E. Corominas and M. Rico-Secades, Evaluaion of a novel Single-Sage High-Power-Facor Elecronic Ballas Based on Inegraed Buck Half-Bridge Resonan Inverer. IEEE APEC'00 pp , New rleans, 000 L 0 D0 C 0 D0 N1 N C 0 C L F R L 0 C0 L 0 (c) V g sin ω D0 C 0 V 0 - (d) Figure 1. Previous high power facor inegraed ballas: boos half-bridge, flyback half-bridge (c) buck-boos halfbridge. (d) Buck half- bridge. L C Q0 Lamp L C Lamp Figure. High power facor inegraed ballas invesigaed in his paper: pre-inegraed Forward half-bridge opology and inegraed Forward half-bridge ballas

5 i L () i Lmed () i g () DTs 1 Ts i gmax i gmed () DT s T s v g () = V g sin ω V /n i g (ω ) θ π Figure 3. Inpu waveforms of he proposed ballas: high frequency and low frequency (filered). PF FP=0.96 θ= θ 150 THD(%) THD=9% θ= Figure 4. Power facor and oal harmonic disorion of he proposed ballas. θ

6 i B1 i B i g () i L () U / - U / i L () i () MDE I MDE III MDE VI MDE II MDE V MDE V Figure 6. peraing waveforms (high frequency) of he proposed ballas for V g >V 0. L C CF i L () MDE I U LA () L i L () C MDE IV i R () LR U LA () L i L () ig() i L () C L F i R () U LA () L C i R () U LA () MDE II MD V L i L () ig() C i R () U LA () D 5 D 4 L i L () C D 7 i R () U LA () MDE III MDE VI Figure 5. peraing modes of he proposed ballas.

7 Figure 7.Elecrical diagram of he prooype Tensión 000/04/6 11:18:34 Corriene Fig. 8. Inpu waveforms: volage, curren 100 V/div, 0. A/div.5 ms/div 000/04/6 17:08:59 U DS I D Fig. 9. Volage and Curren hrough 00 V/div, A/div 5 us/div 000/04/6 17:11:30 Fig. 10. Lamp waveforms: volage, curren and power 100 V/div, 1 A/div, 100 W/div 5 us/div