Volume 5, Numbe, Electonics and elecommunications BAERY AND SUPERCAPACOR CHARGER BASED ON LLC CONVERER Doin PEREUŞ, oma PĂĂRĂU, onuţ COCAN echnical Univesity o Cluj-Napoca, Faculty o Electonics, elecommunications and nomation echnology, 6-8 G. Baiţiu Steet, 47 Cluj-Napoca, Romania, Phone +464445, E-mail: Doin.Cada@ael.utcluj.o Abstact: he need o a small economical powe supply o battey chages has inceased in the last couple o yeas. A LLC convete can be used as a battey chage due to its low E noise, high powe integation and high eiciency. he pape pesents a moe accuate appoach o the design and analysis o the LLC convete. A compaison between the calculations, the simulations and the pactical esults is also pesented. A new analysis and design method which enables the use o the LLC convete as a battey chage and supe capacito chage is pesented. Keywods: esonant convetes, battey chage, ZV, ZC.. NRODUCON Enegy stoage systems like battey and Supe Capacitos became moe and moe impotant in the last couple o yeas. he development o an eicient battey chage cicuit which poduces a vey low amount o E noise is one o the main concens o eseach nowadays. he gowing populaity o the LLC convete in its halbidge implementation is due to its high eiciency, low E emission and the ability to achieve high powe integation. A LLC convete has many advantages ove the othe esonant topologies. t can egulate the output voltage ove a wide ange o load and input voltage vaiations. t can obtain zeo voltage itching ove the entie opeating ange. n many papes [], [] the ist hamonic appoximation is used because it enables the analysis o the LLC convete by means o classical AC cicuit analysis. he ist hamonic appoximation consides the cicuit as a band pass ilte with squae wave excitation. he method consists o eplacing the squae wave input signal with its undamental value [3]. n [-3] a ist hamonic model o the convete is deived and the design method is based then on this model. his pape pesents a moe accuate appoach o the analysis and design o a LLC convete. he esonant tank o the convete consists o thee eactive elements: esonant capacitance C, esonant inducto L and the magnetizing inductance o the tansome L p. As demonstated in [4], [5] thee ae two esonant equencies: one detemined by the esonant capacito C and esonant inducto L and the othe one detemined by the esonant capacito and the magnetizing inductance o the tansome L p in seies with the esonant inductance. = () π C L p = () π C ( L + L ) he convete can wok in thee undamental opeating modes: < p, p < <, >. he convete is designed to wok always in the inductive egion because in the capacitive mode a lage voltage develops acoss the esonant capacito thus a lage enegy level must be ciculating in the esonant tank [6]. he convete must wok always in the inductive egion below, p < <. n this egion the convete can achieve zeo voltage itching (ZVS) o the OSFES and zeo cuent itching (ZCS) o the diodes in the ectie netwok o the entie opeating ange [6], [7]. o do this the convete should wok at the esonant equency at nominal input voltage and ull load. At light load the chaacteistic o a SRC is dominant and at ull load the chaacteistics o a PRC comes on top [8]. he gain chaacteistic o a LLC convete is pesented in Figue. Figue. Chaacteictic o a LLC convete. p anuscipt eceived Apil 6, ; evised June, 6
Volume 5, Numbe, Electonics and elecommunications Figue. Schematic o he LLC convete Fom Figue one can easily see that at the second esonant equency the gain is independent o the load [9]. hese popeties enable the use o the LLC convete in battey and supe capacito chage applications. his pape pesents a new and moe accuate method o the analysis o the esonant convete. Fist the method is descibed then the esults obtained ae compaed with the ones om simulations and the ones om the pactical design.. CONVERER OPERANG PRNCPLES AND DESGN he poposed cicuit is pesented in Figue. he LLC convete consists o thee impotant stages: squae wave geneato, esonant tank and ectie netwok. he unctionality o the LLC convete can be divided in ou stages. he equivalent cicuits as seen om the pimay side o the ou stages ae pesented in Figue 3. Vin L Lp-L nv R a) C Vin L b) Lp-L C Vin Figue 3. Functional stage: a) o the inteval /, b) o the inteval / - w c)o the inteval w - w + /, d) o the inteval w + / - w. L Lp-L nv C c) R L Vin d) Lp-L C he equivalent load esistance R ac as seen om the pimay side can be calculated with []: R ac 8n = R (4) π wee n is the tansome tuns atio and R is the output load. he quality acto Q is: Z = (5) Q R ac he gain o the LLC convete can be expessed as []: m ( ) (, m, Q) = (6) + j ( m ) Q p whee m epesents the atio o the: m = L m /L. he gain chaacteistic o the LLC convete descibed by (6) is pesented in Figue 4. epesents the esonant peiod and w is the itching peiod. Because the esonant equency p is small enough o b) and d) cases the inducto cuent will be consideed constant. he chaacteistic impedance Z o the esonant tank is: L Z = (3) C Figue 4. Gain chaacteistic o the LLC convete. 7
Volume 5, Numbe, Electonics and elecommunications he magnetizing cuent o the tansome eaches its maximum value at a quate o the esonant peiod and is: n V = (7) ( L L ) 4 p wee V is the output voltage o the convete. Consideing the ou stages descibed in Figue 3 the magnetizing cuent is deined ove the entie peiod as ollows: nv + t t Lp L t i m( t) = nv t Lp L + t t + (8) Substituting (9) and () in () and consideing the entie peiod, one can expess the esonant inducto cuent as: = Lt S S t + sin θ LC t + t sin LC θ + t t t () + whee i Lt (t)is the esonant cuent ove the entie peiod. he esonant inducto cuent deived om () is epesented in Figue 6. wee i m (t )epesents the magnetizing cuent and is the itching equency o the squae wave geneato. he magnetizing cuent descibed by (8) is epesented in Figue 5: Figue 6. Resonant inducto cuent. he RS value o the esonant cuent Lms is: Figue 5. agnetizing cuent. he cuent though the esonant inducto the magnetizing cuent is consideed zeo is given by: s av π = n η whee: η = P out /P in. he phase between the two cuents is: (9) θ = actan () S he cuent though the esonant inducto o hal o the esonant peiod, [ - /], consideing the magnetizing cuent also sinusoidal, is: S ( ω θ ) = + sin t L () Lms ( ) ilt = dt (3) he cuent though one tansisto can be easily detemined one consides that the tansisto will be on only one hal o the itching peiod w. = S t t + sin LC t θ t (4) whee i (t) epesents the tansisto cuent. he tansisto cuent descibed by (4) is epesented in Figue 7. he tansisto cuent is null o a hal o the itching cycle. Because the cicuit is woking in the 8
Volume 5, Numbe, Electonics and elecommunications inductive egion the cuent at the beginning o the itching cycle is negative. he aveage cuent though the output diode is: = n η ( ) dt (9) av he RS value o the diode cuent is: Lt m = [ n η ( )] dt () msd Lt m Figue 7. ansisto cuent. he RS value o the tansisto ms is given bylated as: ms ( ) i = dt (5) Because the LLC convete can achieve zeo voltage itching on the entie input ange the itching losses ae zeo. he conduction loss o the tansisto is: P DSon ms = R (6) whee R DSon is the on esistance o the tansisto. he junction tempeatue o the diode can be calculated as: J = + R P (7) A thja Consideing the cuents calculated in (8) and (9) the powe loss due to the diode can be expessed as: P D F av d msd = V + () whee V F is the owad voltage dop and d the on esistance o the diode. he calculated powe is used to detemine the type o diode used and can also be used to detemine the maximum junction tempeatue. he junction tempeatue o the diode can be calculated with: JD = + R P () A thja whee JD is the junction tempeatue o the diode, R thja is the junction to ambient themal esistance o the diode and A epesents the ambient tempeatue. A theoetical method o chaging a battey o a supecapacito can be to implement a chaging algoithm in two steps, as in Figue 9 []. D wee J is the junction tempeatue o the OSFE tansisto, A is the ambient tempeatue and R thja is the themal junction to ambient esistance o the tansisto. he cuent though the ectie diodes can be expessed as the deence between the esonant cuent and the magnetizing cuent: i = n η ( i ( )) (8) D Lt m t he cuent though both diodes is shown in Figue 8. Figue 9. Battey chage chaacteistic Figue 8. Diode cuent. he battey/supecapacito is chaged ist with a constant cuent, supplied to the battey until the voltage eaches a theshold given by the poduce o the battey/ supecapacito. n the second step, the voltage on the battey/supecapacito is kept constant until the cuent dops below a theshold value which is pescibed by the designe. his theshold is usually.5c o common batteies. 9
Volume 5, Numbe, Electonics and elecommunications Figue. Contol cicuit. he contol cicuit is designed to keep the cuent constant when the voltage o the battey o supe capacito is below the pescibed value, step, and to keep the voltage constant when the battey/supecapacito voltage theshold is eached, step. When the output cuent o the LLC convete is lowe than the pescibed cuent o the loop D is o, D is on and the convete woks as a constant voltage souce. n this mode the voltage loop egulates the output voltage and the cuent loop is disabled. When the cuent is lage than the cuent pescibed diode D is o D is on and the convete woks as constant cuent souce. n this mode the cuent loop keeps the cuent constant and the voltage loop is disabled. An optocouple is used to ensue galvanic sepaation between the input and the output o the LLC convete end to satisy the saety standads o electical secuity. his eatue togethe with the ability to achieve high powe integation and high eiciency enable the use o the LLC convete as a battey chage and also a supe capacito chage.. SULAON RESULS OF HE CONVERER A simulation model o the LLC convete was build with the ollowing input paametes: V out = V, out =.5A, P out = 5W. he calculated values o the esonant tank ae: L = 69uH, L p = 79uH, C =9.4nF. he magnetizing cuent calculated with (8) o V in = 35V, is pesented in athcad Figue a), togethe with PS simulation Figue b). As one can seen om Figue, the cicuit is woking below the second esonant equency and even the magnetizing cuent is consideed constant om to the appoximation is vey close to the simulation esult. Figue. agnetizing cuent: a) athcad, b) PS Consideing V in = 4V he magnetizing cuent is obtained as epesented in Figue. Figue. agnetizing cuent: a) athcad; b) PS. he esonant cuent obtained epesenting () o the designed convete in athcad is pesented in Figue 3 a)
Volume 5, Numbe, Electonics and elecommunications togethe with the PS simulation esults Figue 3 b). he esults ae obtained o V in =35V. Figue 3. Resonant cuent: a) athcad; b) PS. Consideing V in = 4V he esonant cuent is obtained as epesented in Figue 4. Figue 6. ansisto cuent: a) athcad; b) PS. he cuent though the diodes obtained epesenting (8) o the designed convete in athcad is pesented in Figue 7, togethe with the PS simulation esults. Figue 4. Resonant cuent: a) athcad; b) PS. he cuent though the OSFE obtained epesenting (4) o the designed convete in athcad is pesented in Figue 5 a), togethe with the PS simulation esults, in Figue 5 b). he esults ae obtained o V in = 35V. Figue 7. Diodes Cuent: a) athcad; b) PS. Consideing V in = 4V the OSFE cuent is obtained as epesented in Figue 8. Figue 5. ansisto cuent: a) athcad; b) PS. Consideing V in = 4V he OSFE cuent is obtained as epesented in Figue 6. Figue 8. Diodes Cuent: a) athcad, b) PS he chaacteistic o the chage is pesented in Figue 9. he chage keeps the cuent constant until the voltage is V and then the cuent dops to and the voltage is kept constant.
Volume 5, Numbe, Electonics and elecommunications Figue. Diode cuent. Figue 9. Chage chaacteistic. V. EASUREENS A LLC convete with the ollowing paametes was ealized: : V out = V, out =.5A, P out = 5W. he waveom o the esonant cuent consideing V in = 35V is epesented in Figue a) and o V in = 4V in Figue b). V. CONCLUSONS he pape pesents a method o the design and analysis o a battey chage based on a LLC convete. he LLC convete is suited o battey chage applications due to its low E emission and the ability to achieve high powe integation and high eiciency. n many papes the ist hamonic appoximation is used o the design o the convete because it enables the analysis o the LLC conveto by means o classical AC cicuit analysis. his pape pesents a moe accuate method o the design and analysis o the LLC convete. he simulation end expeimental esults validate the poposed method. he poposed contol method o the LLC convete enables the use o the convete as a battey chage, and also as a supecapacito chage. ACKNOWLEDGEEN his wok was suppoted by CNCSS UEFSCSU, poject numbe 79/..7 o the PN DE D_9/7 pogam. Figue. Resonant cuent. he waveom o the esonant cuent consideing V in = 35V is epesented in Figue a) and o V in = 4V in Figue b). Figue. ansisto cuent. he waveom o the esonant cuent consideing V in = 35V is epesented in Figue a) and o V in = 4V in Figue b). REFERENCES [] Faichild Semiconducto Cop., "Hal-Bidge LLC Resonant Convete Design Using FSFR-seies Faichild Powe Switch", Appl. Note 45, pp. -7, 7. [] Sicoelectonics, "LLC Resonant Hal-bidge Convete Design Guideline", Appl. Note 45, pp. -3, 7. [3] ON Semiconducto, "A Simple DC SPCE odel o the LLC Convete", Appl. Note 855D, pp. -, 6. [4] ingping ao, Dimita chobanov, Dong Li, atin aez, obias Gebe, Geald Deboy, Leo Loenz, "Analysis and Design o a Hz LLC Resonant Convete with Coeless ansome Dive", ntenational Coneence & Exhibition o Powe Electonics, China, 7. [5] ON Semiconducto, "Undestanding the LLC Stuctue in Resonant Applications", Appl. Note 83D, pp. -6, 8. [6] Sicoelectonics, "An ntoduction to LLC Resonant Hal Bidge Convete", Appl. Note 644, pp. -64, 7. [7] Yu Fang, Dehong Xu, Yanjun Zhang, F. Gao, L. Zhu, "Design o High Powe Density LLC Resonant Convete with Exta Wide nput Range", he nd Annual Applied Powe Electonics Coneence and Exposition, Austalia, pp. 976-98, 7. [8] Bo Yang, "opology nvestigation o Font End DC/DC Powe Convesion o Distibuted Powe System", Ph.D. thesis, Viginia Polytechnic nstitute and State Univesity, Blacksbug, Viginia, 3. [9] Ya Liu, "High Eiciency Optimization o LLC Resonant Convete o Wide Load Range",.S. thesis, Viginia Polytechnic nstitute and State Univesity, Blacksbug, Viginia, 7. [] Cada Doin, Peteus Doin, Ciocan onuţ, Doba Petu, "An mpovement on Empiical odelling o the Batteies", he 3 nd ntenational Sping Semina on Electonics echnology, Bno,
Volume 5, Numbe, Electonics and elecommunications Czech Republic, 9. [] W. Chen, Z. Y. Lu, X. F. Zhang and S. S. Ye, "A Novel ZVS Step-up Push-pull ype solated LLC Seies Resonant DC-DC Convete o UPS Systems and its opology Vaiations", he 3 d Annual Applied Powe Electonics Coneence and Exposition, Austin, pp. 73-78, 8. [] B. Yang, F. C. Lee, A. J. Zhang and G. Huang, "LLC Resonant Convete o Font end DC/DC Convesion", he 3 d Annual Applied Powe Electonics Coneence and Exposition, Dallas, pp. 8,. [3]. Bataseh, R. Liu, C. Q. Lee and A. K. Upadhyay, "heoetical and Expeimental Studies o the LCC-type Paallel Resonant Convete, EEE ansactions on Powe Electonics, Vol. 5, ssue, pp. 4-5, Apil, 99. [4] A. J. Gilbet, C.. Bingham, D. A. Stone and. P. Foste, "Nomalized Analysis and Design o LCC Resonant Convetes", EEE ansactions on Powe Electonics, Vol., ssue 6, pp. 386-4, Novembe 7. [6]. P. Foste, H.. Sewell, C.. Bingham, D. A. Stone and D. Howe, "ethodologies o the Design o LCC Voltage-Output Resonant Convetes", Poceedings o the EEE Elect. Powe Appl., Vol. 53, ssue 4, pp. 559-567, July 6. [7] D. Fu, F. C. Lee, Q. Yang and F. Wang, "A Novel High- Powe-Density hee-level LCC Resonant Convete with Constant-Powe-Facto-Contol o Chaging Applications", EEE ansactions on Powe Electonics, Vol. 3, ssue 5, pp. 4-4, Sept. 8. 3