Design of an LLC Resonant Convete Using Genetic Algoithm H. H. Nien, C. K. Huang, S. K. Changchien, C. H Chan Dept. of Electical Engineeing, Chienkuo Technology Univesity E-mail: nien@ctu.edu.tw Dept, of Industial Education Technology, National Changhua Univesity of Education E-mail: ckhuang@cc.ncue.edu.tw Abstact With the featue of soft switching, LLC esonant convetes pesent the advantages of high convesion efficiency low electomagnetic intefeence that it is applicable to powe convetes. Howeve, since the output cuent ipples ae lage, LLC esonant convetes would equie lage output capacitos to achieve the featue of high DC output quality. With the application of esonant cicuits, the povided cuent shaping netwok has ovecome the above dawbacks; howeve, thee is still no design ule fo esonant element paametes. Fo this eason, this study aims to develop a seies of methods fo the design of esonant element paametes to seek fo the optimal output cuent modification so as to achieve the pupose with the lowest output cuent ipples. The expeimental esults show that it can effectively educe the output cuent ipples up to 0.4%, when the output is fully loaded. Keywods:. LLC esonant convetes, output cuent ipples, esonant element paametes, genetic algoithm Intoduction In ecent yeas, consume electonic poducts pesent sticte equiements on powe adapte fo the puposes of enegy saving, envionmental potection, hiness. Diffeent fom the low powe of switching powe supply convetes o high powe, but equiing cooling fans, of desktop compute poducts fo geneal consume electonic poducts, the powe supplies fo liquid cystal display televisions ae mostly with high powe output but without cooling fans. In this case, the design of powe supply fo LCD televisions must be hy with high convesion efficiency. Futhemoe, it has to avoid noise o snowflakes esulted fom the intefeence of high fequency fom powe supplies on LCD televisions. Fo this eason, the achitectue of LLC esonant convetes has become moe emphasized. F. C. Lee poposed the convetes with quasi-esonant multi-esonant in 988,, fo the fist time, applied zeo-voltage multi-esonant convetes []. In the same yea, R. Liu, C. Q. Lee poposed the multi-esonant technology in LLC seies esonant convete (LLC-SRC to pove that LLC-SRC outpefomed taditional SRC, futhe applied the analyses of invete contol mathematical model to complete the LLC-SRC with half-bidge 00W single output. R. Liu futhe inceased the output powe to 50W fo the multi-output LLC-SRC so that the achitectue of LLC-SRC became moe emphasized [-4]. Thee have been seveal liteatues on the achitectue of LLC esonant [5-]. Viewpoints on esonant tank with vaious combinations o the pomotion of switching fequency efficiency ae poposed to make the achitectue of LLC esonant moe complete fo wide applications [-5]. With the advantage of zeo-voltage switch, the convesion efficiency of LLC-SRC is high, but the output cuent ipples ae elatively lage. Fo this eason, a lage output capacito is equied fo LLC-SRC to achieve the featue of high DC output quality [6-9]. Nevetheless, having additional esonant cicuits to modify output cuent could educe cuent ipples, but thee has not been an effective method to design the esonant cicuit elements that mismatching esonant cicuits could incease cuent ipples. Fo this eason, this study poposes to apply genetic algoithms to design esonant netwok elements to obtain the optimal theoetical values of esonant elements with the optimal design of genetic algoithms. Finally, this study completes the LLC-SRC pototype cicuits with cuent modification, futhe eceives the esults fom cicuit expeiments measues show that the output cuent ipples ae effectively contolled, the output capacito value is educed. Cicuit Configuation Resonant convetes combine inductos capacitos in the esonant cicuits futhe implement zeo-voltage switching o zeo-cuent switching by contolling the switching time to achieve the pupose of educing switching loss. Moeove, esonant convetes incopoate paasitic capacitos stay inductos into esonant tank without educing the cicuit pefomance. Figue shows typical voltage gain chaacteistics fo an LLC esonant convete. When LLC is opeated in egion with output cuent being DCM, lage output cuent ipples would be geneated. Fo this eason, lage capacitos ae geneally equied to achieve the high DC output quality. Fo futhe impovements, cuent modifications ae often peceded by paallel connection with a set of lossless passive elements in the esonant tank of pimay side to educe output cuent ipples futhe achieve the highe DC output quality. Since thee ae hadly any voltage suges in the pocess of diodes switching, diodes with double withsting voltage to the
output voltage ae commonly applied. Nonetheless, the poblem of fowad voltage dop esulting in conducting loss, when the diodes ae conducted, should be taken into consideations. Fig. Typical opeation egions of an LLC esonant convete Fig. shows an LLC esonant convete with cuent shaping its equivalent cicuit. Fig. Cuent shaped LLC esonant convete equivalent cicuit The output cuent i is o i ( t = i ( t + i ( t = ni ( t = n i ( t i ( t o D D p L Lm,( whee i D ae diode cuents, n is tun atio, ip ( t is ideal pimay cuent, il ( t is esonant inducto cuent, ilm ( t is exciting cuent of the tansfome. The peak output cuent I o,max occus when the pimay cuent is maximum ( I p,max. When powe switch Q is on initial values il( t0 = ILt0, vc ( t0 = VCt0, il ( t0 = ILt 0, vc( t0 = VC t0 i ( t = I, then Lm 0 Lmt0 dil Vin = L + nvo + vc ( dvc dvc i L C C (3 dil vc = vc+ L (4 dv i C C L = (5 V + V + C L ( V nv V i ( t = ( C + C { sin[ ( tt ] L Ct 0 Ct0 in o Ct 0 CL ( 0 Lt 0( + Lt0 cos[ ( t C CL ( t0] C0 t Ct0+ ( in o C0 t sin[ ( t t0] CL ( Lt 0( + Lt0 cos[ ( tt0]} C CL ( VCt 0+ VCt0+ CL ( VinnVoVCt 0 3 { sin[ ( CL ( 0] Lt 0( + Lt0 3 cos[ ( t t0] C CL ( C0 t Ct0+ ( in o C0 t 3 sin[ ( tt0] CL ( Lt 0( + Lt0 3 cos[ ( t C CL ( t0]} + V V C L V nv V + + CC L tt V V C L V nv V + (6 nvo ilm( t = ( t t0 + ILmt0 (7 L m i ( t = i ( t i ( t (8 p L Lm 3 Design Pocedue This pape designs an LLC esonant convete opeating in egion ; meanwhile genetic algoithm is applied to calculate the optimal theoetical values of esonant elements to complete the convete cicuit pototype. 3. LLC esonant convete Steps of detemination of esonant components fo egion opeating ae shown as followed. Step : Set the gain calculate the tuns atio. Step : Select the appopiate Q. An appopiate Q can avoid the powe switches to opeate at zeo cuent switching. Step 3: 3-: choose the fist esonant fequency f, as opeating in egion, the full-load switching fequency f s, full is empiically 0.7 f ~0.8 f. 3-: choose appopiate powe switches with adequate withst voltage withst cuent, acquie the paasitic capacitance the on-esistance. Step 4: Detemine esonant tank L C. Howeve, the theoetical capacitance of C obtained fom theoetical analysis is confined to the pactical specifications, theefoe an appoximately actual capacito which is much less than the theoetically maximum capacito can only be selected. Step 5: Select the appopiate value K fo detemination of magnetizing inducto L m 3. Genetic Algoithm The genetic algoithm (GA contains poweful opeatos, the most fundamental of them being epoduction, cossove, mutation. If easonable fitness functions ae detemined these thee opeatos ae appopiately employed, the optimal solution of the theoetical value of cicuit elements can be obtained.
Figue shows a flowchat fo genetic algoithm. If easonable fitness functions ae detemined these thee opeatos ae appopiately employed, the optimal solution of the theoetical value of cicuit elements can be obtained. function. Theefoe, L, chomosomes. C C ae selected as the Refeing to most applications, we detemine the anges fo the cicuit elements as L [0 μ H ~ 0 μ H], ~0.μ F], C [5 nf ~ nf] C [5 nf ~ n F]. The population size, cossove pobability, mutation pobability of GA ae 60, 0.5, 0.008, espectively. Accoding to the design pocedue (Figue, the values fo genes ae fist given by binay encoding of the octal (paent geneation. The best genes ae then etained to the next geneation fo double cossove. New geneations ae poduced, among which we omly select genes fo mutation. Step by step, we each the optimal theoetical values. In the last stage, afte 40 geneations of encoding, epoduction, cossove, mutation, we obtain the esults as shown in Fig. 3. The lowest p. peak i is 5. A. As such, the optimal theoetical values fo the cicuit elements ae L =00.5 μ H, C =0.6 n F C =9.8 F n. Fo pactical elements, we choose C =0 n F C =0 n F. Fig.. Optimal design flowchat fo genetic algoithm. 4 Design Example Table is the design specifications fo the LLC esonant convete. L6599 (STMicoelectonics is adopted as the contol IC. Table Specifications fo the LLC esonant convete Paamete Value LLC Resonant Convete Region Resonant Elements V in V o D Po f f s L m L C 380 V 4 V 0.5 40 W 00 khz 75 khz 67 uh 3.4 uh nf Fom the equations in section, the cicuit elements L, C C can affect ip ( t (fitness Fig. 3. Simulation of fitness values by genetic algoithm. 5 Measuements Discussions The dive signal, the switch voltage switch cuent wavefoms of powe switch Q Q fo with without cuent shaping cicuit ae shown in Figue 4. The measued switching fequency ( fs = 73.8 khz the calculated switching fequency ( fs = 75 khz is vey simila when the convete opeates at full load. Among them, thee ae no ovelaps between v GS v DS, pove that thee ae no powe switch switching losses. So the powe switches achieve zeo-voltage switching, which impoves oveall efficiency. Figue 5 eveals esonant inducto cuent i L the output cuent i o when opeated at full load. As thee is no evese ecovey cuent poblem, diodes have eached zeo-cuent switching. When the esonant inducto cuent the magnetizing inducto cuent ae equal, the tansfome pimay cuent is zeo. Since thee is almost no voltage suge on diodes when switching, it is geneally selected the withst voltage of diodes is twice the output voltage. The only still consideation is the diode conduction loss.
has been significantly impoved to 5.6 A. Figue 6 shows the compaison of peak output cuents fo LLC convetes with without cuent shaping netwok. Afte adding esonant netwok, the capacitos C C esonate with L, shae the cuent on C, modify the cuent wavefom of esonant inducto i L, theeby educe the peak output cuent i o,max. Figue 7 demonstates eduction ates of the measued peak output cuents fo the optimal cicuit design fom 0% load to full load. Fo most loads, thee ae at least 5% eductions a maximum eduction of 0.4% occued at full load. Fig. 6. Compaison of peak output cuents fo LLC convetes with without cuent shaping netwok at diffeent loads. Fig. 4. Measued wavefoms of powe switch Q Q at full load: (awithout,(bwith cuent shaping, (c, (d zoom-in chats to pove ZVS of Q Q Fig. 7. Reduction ates of the measued peak output cuents by using the optimal cicuit design. Fig. 5. Measued wavefoms of the esonant inducto cuent i L the output cuent i o when opeated at full load:(awithout,(bwith cuent shaping. Table is the expeimental esults of LLC esonant convete with cuent-shaping netwok designed by the poposed method. In ode to pove that the convesion efficiency is not affected by the added cuent-shaping netwok, the changes of the two LLC esonant convetes ae the esonant inducto L, esonant capacitos C C, the othe cicuit elements maintain the same. The maximum efficiency is 94.0% when output cuent is 4A. And the full load efficiency is of 9.9%. Table Measued efficiencies of LLC esonant convete with cuent-shaping netwok. The tansfome pimay cuent i p is zeo when i L is equal to the magnetizing inducto cuent i Lm. The tansfome can be egaded as open no enegy tansfeed to the output side though the tansfome at that time, so i o is zeo. The peak of i o without cuent shaping is 9.6 A. Meanwhile, fom figue 5(b, the peak output cuent of i o, modified by adding the cuent shaping netwok,
6 Conclusions This pape poposes an effective method fo educing the LLC esonant convete output cuent ipple. In the wok, the genetic algoithm is fistly conducted to detemine the value of the esonant netwok components. Although genetic algoithms can obtain the ideal optimum values, in fact, the actual cicuit exists non-ideality factos of the paasitic components. Theefoe, thee ae eos associated with the actual values. Howeve, cicuit elements can still be significantly optimized though genetic algoithms design. In this study, the theoetical optimal output cuent peak value is 5.A the expeimental esult is 5.6A which has damatically educed the output cuent ipple. Refeences [] F. C. Lee, "High-Fequency Quasi-Resonant Multi-Resonant Convete Technologies," Annual Confeence of Industial Elect- onics Society, vol. 3, pp. 509-5, 988. [] R. Liu, C. Q. Lee, "Analysis design of LLC-type seies esonant conveto," Electonics Lettes, vol. 4, pp. 57-59, 988. [3] R. Liu C. Q. Lee, "The LLC-type seies esonant convete -vaiable switching fequency contol," Poceedings of the 3nd Midwest Symposium on Cicuits Systems, vol., pp. 509-5, 989. [4] R. Liu, C. Q. Lee, A. K. Upadhyay, "Expeimental study of the LLC-type seies esonant convete," Applied Powe Electonics Confeence Exposition, pp. 3-37, 99. [5] B. Yang, F. C. Lee, A. J. Zhang, G. Huang, "LLC Resonant Convete fo Font End DC-DC Convesion," Applied Powe Electonics Confeence Exposition, vol., pp. 08-, 00. [6] G. C. Hsieh, C. Y. Tsai, S. H. Hsieh, "Design Consideations fo LLC Seies-Resonant Convete in Two-Resonant Regions," Powe Electonics Specialists Confeence, pp. 73-736, 007 [7] H. Choi, "Analysis Design of LLC Resonant Convete with Integated Tansfome," Applied Powe Electonics Confeence, pp. 630-635, 007 [8] B. Yang, R. Chen, F. C. Lee, "Integated magnetic fo LLC esonant convete," Applied Powe Electonics Confeence Exposition, vol., pp. 346-35, 00. [9] B. Yang, F. C. Lee, M. Concannon, "Ove cuent potection methods fo LLC esonant convete," Applied Powe Electonics Confeence Exposition, vol., pp. 605-609, 003. [0] G. C. Hsieh, C. Y. Tsai, W. L. Hsu, "Synchonous Rectification LLC Seies-Resonant Convete," Applied Powe Electonics Confeence, pp. 003-009, 007. [] J. H. Jung, J. G. Kwon, "Theoetical analysis optimal design of LLC esonant convete," Euopean Confeence on Powe Electonics Applications, pp. -0, 007. [] A. J. Fosyth, G. A. Wad, S. V. Mollov, "Extended fundamental fequency analysis of the LCC esonant convete," Tansactions on Powe Electonics, vol. 8, pp. 86-9, 003. [3] Y. Ma, X. Xie, Z. Qian, "Fequency-Contolled LCC Resonant Convete with Synchonous Rectifie," 7th Intenational Confeence on Powe Electonics Dive Systems, pp. 44-445, 007. [4] Y. Ang, C. M. Bingham, M. P. Foste, D. A. Stone, "Modelling Regulation of Dual-Output LCLC Resonant Convetes," 33d Annual Confeence of the IEEE, Industial Electonics Society, pp. 30-35, 007. [5] E. S. Kim, H. K. Lee, Y. S. Kong, Y. H. Kim, "Opeating Chaacteistics in LCLC Resonant Convete with A Low Coupling Tansfome," Applied Powe Electonics Confeence, pp. 65-656, 007. [6] F. Dianbo, L. Bing, F. C. Lee, "MHz High Efficiency LLC Resonant Convetes with Synchonous Rectifie," Powe Electonics Specialists Confeence, pp. 404-40, 007. [7] L. Teng, Z. Ziying, X. Aiming, Z. John, J. Ying, "A Novel Pecise Design Method fo LLC Seies Resonant Convete," 8th Annual Intenational, Telecommunications Enegy Confeence, pp. -6, 006. [8] F. Dianbo, L. Ya, F. C. Lee, X. Ming, "An impoved novel diving scheme of synchonous ectifies fo LLC esonant convetes," Applied Powe Electonics Confeence Exposition, pp. 4-8, 008. [9] H. De Goot, E. Janssen, R. Pagano, K. Schettes, "Design of a -MHz LLC Resonant Convete Based on a DSP-Diven SOI Half-Bidge Powe MOS Module," Tansactions on Powe Electonics, vol., pp. 307-30, 007.