Research Article Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

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1 The Scienific World Journal Volume 013, ricle I 61896, 11 pages hp://dx.doi.org/ /013/61896 esearch ricle omparison beween Phase-Shif Full-ridge onverers wih Noncoupled and oupled urren-oubler ecifier heng-tao Tsai, 1 Jye-hau Su, and Sheng-Yu Tseng 3 1 eparmen of Elecrical Engineering, Naional hin-yi Universiy of Technology, Taichung 41170, Taiwan eparmen of Elecronic Engineering, Naional hin-yi Universiy of Technology, Taichung 41170, Taiwan 3 eparmen of Elecrical Engineering, hang-gung Universiy, Tao-Yuan 33344, Taiwan orrespondence should be addressed o Jye-hau Su; jc07@ms34.hine.ne eceived 31 July 013; cceped 0 Ocober 013 cademic Ediors: G. e Mey, S.. Mahmoud, and G. Priebe opyrigh 013 heng-tao Tsai e al. This is an open access aricle disribued under he reaive ommons ribuion License, which permis unresriced use, disribuion, and reproducion in any medium, provided he original work is properly cied. This paper presens comparison beween phase-shif full-bridge converers wih noncoupled and coupled curren-doubler recifier. In high curren capabiliy and high sep-down volage conversion, a phase-shif full-bridge converer wih a convenional currendoubler recifier has he common limiaions of exremely low duy raio and high componen sresses. To overcome hese limiaions, a phase-shif full-bridge converer wih a noncoupled curren-doubler recifier (N) or a coupled curren-doubler recifier () is, respecively, proposed and implemened. In his sudy, performance analysis and efficiency obained from a 500 W phase-shif full-bridge converer wih wo improved curren-doubler recifiers are presened and compared. From heir prooypes, experimenal resuls have verified ha he phase-shif full-bridge converer wih N has opimal duy raio, lower componen sresses, and oupu curren ripple. In componen coun and efficiency comparison, has fewer componens and higher efficiency a full load condiion. For small size and high efficiency requiremens, is relaively suiable for high sepdown volage and high efficiency applicaions. 1. Inroducion In a decenralized power sysem, he fron end ac/dc converer is generally composed of wo sages, in which one is a power facor correcion (PF) and he oher is an inermediae dc/dc converer, as shown in Figure 1. Mos of PF circuis adop a boos converer [1], and an inermediae converer is usually wih an isolaed version []. Using a boos converer can achieve a uniy power facory, and using an isolaed converer can provide galvanic isolaion and high oupu curren. In off-line applicaions, universal ac volage is always ino dc 400 V as a dc bus by boos converers, and an inermediae dc/dc converer convers i o a low volage bus of 4 V dc or 1 V dc. Therefore, for high oupu curren and low oupu volage applicaions, an isolaed dc/dc converer is usually required. To achieve low oupu volage, high oupu curren, and high efficiency, a phase-shif full-bridge converer wih convenional curren-doubler recifier is widely used in mediumhigh power condiion, as shown in Figure [3]. Neverheless, i sill has several limiaions. For example, for high sepdown volage conversion, i requires a ransformer wih high urns raio or i has o reduce he duy raio of he swiches. high urns raio will resul in high duy loss and low conversion efficiency, while a low duy raio will increase inpu peak curren and componen sress [4]. The oher limiaion is ha is large exernal resonan inducor will induce a large circulaion curren, which will flow hrough he primary winding of he ransformer and he swiches during a freewheeling inerval. s a resul, conducion loss in he swiches and copper loss in he ransformer are significan. To release he above-menioned limiaions of he convenional full-bridge converer wih curren-doubler, many approaches have been conduced [3 7]. However, heir high sep-down volage raio sill resul in exremely low duy raio, which will induce high peak curren hrough he secondary winding of he isolaion ransformer and oupu filer inducors, increasing copper loss and componen sresses [8 1]. To solve he above-menioned problem, he phase-shif full-bridge converer wih N or is proposed,

2 The Scienific World Journal PF Preregulaor 400 V High sep-down / converer 4 V/1 V Figure 1: Two-sage srucure of preregulaor. onvenional currendoubler recifier V in Q Q b N p N s Q Q L 4 Figure : The phase-shif full-bridge converer wih convenional curren-doubler recifier. Noncoupled curren-doubler recifier Q Q r3 L 1 b N p N s L Vo V in Q Q r4 L 4 Figure 3: The proposed phase-shif full-bridge converer wih N. asshowninfigures3 and 4 [13]. They can alleviae he drawbacks of exremely low duy raio and high componen sresses. The wo proposed improved recifiers can exend duy raio of he acive swiches o reduce he peak curren hrough he secondary winding of he ransformer and lower oupu curren ripple. The conversion efficiency can be increased significanly. Secion describes derivaion and operaional principle of he wo proposed improved currendoubler recifiers. Secion3 compares he benefis of he wo improved curren-doubler recifiers. Power loss and efficiency esimaion are described in Secion 4. Experimenal resuls obained from a 500 W phase-shif full-bridge converer wih N and are presened in Secion 5. Finally, a conclusion is given in Secion 6.. erivaion of Improved urren-oubler ecifiers Wih dualiy mehod, N can be derived from a volagequadrupler circui, and coupled-doubler can be derived from a volage-doubler circuis. In he following, derivaions of boh improved curren-doubler recifiers are described in deails..1. erivaion of N. erivaion of N is based on a convenional volage-quadrupler circui, as shown in Figure 5. ccording o dualiy principle, meshes of he volage quadrupler are replaced wih nodes, and capaciors

3 The Scienific World Journal 3 oupled-curren-doubler recifier V in Q 1 1 r1 Q 3 b L r3 11 L r V N sec p N s o Q r Q 4 r4 4 Figure 4: The proposed phase-shif full-bridge converer wih. 1 r Tr L 1 r3 r4 6 r4 6 4 L 4 Figure 5: erivaion of N from a volage-quadrupler based on dualiy principle: volage-quadrupler and N. are replaced wih inducors, while diodes are wih no change, yielding he proposed N as shown in Figure 5... erivaion of. Similarly, derivaion of is based on a convenional volage-doubler circui, as shown in Figure 6. ccording o dualiy principle, meshes of he volage doubler are replaced wih nodes, and capaciors are replaced wih inducors, while diodes are wih no change, yielding he convenional curren-doubler recifier as shown in Figure 6. Uilizing coupled inducor concep, he oupu filer inducors can be exended o he coupled ones, as shown in Figure 6(c). 3. Operaional Principles of N and ForNand,eachofwhichhasisownmeris and demeris. To have an objecive judgmen, operaional principles of N and are briefly described as follows Operaional Principle of N. In Figure 3,heproposed phase-shif full-bridge converer wih N under coninuous inducor curren operaion can be divided ino four major operaing modes over a half swiching cycle. Figure 7 shows concepual volage and curren waveforms relaive o key componens of N. eff and loss are denoed as he effecive and loss duy raios, respecively. V is he volage across he resonan inducor and he isolaion-ransformer primary winding, is he volage across he isolaionransformer secondary winding, is he secondary curren, and i L are he curren of he energy inducors, i L3 and i L4 are he curren of he oupu filer inducors, and i 1 i 4 are he curren of he recifier diodes. To simplify descripion of he seady-sae operaional modes, he phase-shif fullbridge converer will no be discussed in his secion. Only heproposednisanalyzed.underconinuousinducor curren operaion, four major operaing modes of he N areidenifiedoverahalfswichingcycle.figure 8 shows equivalen circuis of he N operaional modes. Mode 1 (Figure 8, 0 < 1 ).ime 0, a posiive volage crosses he secondary winding of ransformer.firs of all, diode r3 is reversely biased and,,and r4 are conducing. uring his inerval, inducor curren i L3 flowing hrough he pah is linearly increased, and inducor currens and i L4 are linearly decreased. Mode (Figure 8, 1 < ).ime 1,hesecondary curren is equal o inducor curren i L3,anddiode is

4 4 The Scienific World Journal L r1 T 3 r Tr 4 3 L 11 L 1 4 (c) Figure 6: erivaion of from a volage-doubler based on dualiy principle: volage-doubler, convenional curren-doubler recifier, and (c). V T/ T loss T eff T winding of ransformer, since recifier diode currens i r3 and i r4 have no been commuaed compleely ye. Therefore, all of he diodes ( r4 ) are mainained conducing, while inducor currens i L3 and i L4 are mainained discharging o he load. ime 4, recifier diode currens i r3 and i r4 have been commuaed compleely. Then, a posiive volage crosses he secondary winding of ransformer.thisendsahalf swiching cycle operaion. i L i L4 i L3 V r V r 1 i r 1 i r i r 4 V r 3 V r 4 i r Figure 7: Key waveforms of he proposed phase-shif full-bridge converer wih N. reversely biased. Inducor curren i L =i L3 flowing hrough he pah is linearly increased, while he energy sored in inducor L 1 and L 4 will be released hrough he recifier diode and r4 o he load, respecively. Mode 3 (Figure 8(c), < 3 ).Whenvolage drops o zero a ime, all of he diodes ( r4 )areconducing. uring his inerval, he inducor curren i L3 flowing hrough wo pahs - r3 - and and he inducor curren i L4 flowing hrough - r4 -L 4 are linearly decreased. Mode 4 (Figure 8(d), 3 < 4 ).ime 3, a negaive volage V will cross he resonan inducor and he primary 3.. Operaional Principle of. In Figure 4,eachcoupled inducor individually funcions as a apped inducor or a ransformer during one swiching cycle. In oher words, he upper coupled-inducor is charged during he charging period, which funcions as a apped inducor, while he lower coupled-inducor funcions as a ransformer. Therefore, Figure 4 can be redrawn as shown in Figure 9. The proposed phase-shif full-bridge converer wih under coninuous inducor curren operaion can be divided ino hree major operaing modes over a half swiching cycle. Figure 10 shows concepual volage and curren waveforms relaive o key componens of he converer. eff and loss are denoed as he effecive and los duy raios, respecively. V is he volage across he resonan inducor and he isolaion-ransformer primary winding, is he volage across he isolaion-ransformer secondary winding, is he secondary curren, i L and V L arehecurrenandvolageofhe coupled-inducor winding n 1, i r and V r are he curren and volage of he recifier diode, and i o is he oupu curren. The circui operaion is explained as follows. Mode 1 (Figure 11, 0 < 1 ).ime 0,currens i r1 and i r are commuaed compleely. Then, a posiive volage crosses he secondary winding of ransformer ;diode is reversely biased, and inducor curren flowing hrough he pah of L 11 -L 1 increases linearly. uring his inerval, he energy sored in inducor will be released o he load hrough coupled inducor, and inducor curren i L flowing hrough he pah of - is decreased. Meanwhile, inducors L 11 and L 1 funcion as

5 The Scienific World Journal 5 i L3 i L3 V T L 1 r N p N s L i L r3 i L4 o V N p L 1 N s i L r3 i L4 o r4 L 4 r4 L 4 i L3 i L3 V N p L 1 N s i L r3 i L4 o V N p Tr L 1 N s i L r3 i L4 o r4 L 4 r4 L 4 (c) Figure 8: Operaional modes of he proposed full-bridge phase-shif converer wih N: mode 1, mode, (c) mode 3, and (d) mode 4. oupled-curren-doubler recifier (d) V in Q 1 1 r1 Q 3 r3 3 b N p L 11 L 1 r1 o N s Q r Q 4 r4 4 Figure 9: Each coupled inducor individually funcions as a ransformer for. a apped inducor, while inducors and are coupled o funcion as a ransformer T. Mode (Figure 11, 1 < ).Whenvolage drops o zero a ime 1, he energy sored in inducor is no longer released o he load hrough coupled inducor. Therefore, inducor curren i L will be gradually decreased, recifier diodes and are conduced, and recifier diode currens i r1 and i r begin commuaing. uring his free-wheeling inerval, inducor currens and i L decrease linearly. Mode 3 (Figure 11(c), < 3 ). ime, a negaive volage V will cross resonan inducor and he primary winding of ransformer, since recifier diode currens i r1 and i r have no been commuaed compleely ye. Therefore, he wo recifier diodes and are mainained conducing, while inducors L 1 and are discharged hrough diodes and,respecively. When currens i r1 and i r are commuaed compleely a ime 3, he converer operaion over a half swiching cycle is compleed. 4. Performance omparison beween N and This secion will compare boh he feaures and characerisics of N as well as, which include secondary

6 6 The Scienific World Journal T/ T (( 1 ) )T loss T eff T V V L1 V L Inducor acion Transformer acion i L Transformer acion Inducor acion i o i r i r Figure 10: Key waveforms of phase-shif full-bridge converer wih. winding peak curren of ransformer, volage gain, and oupu curren ripple Performance of N. From Figures 3 and 7, during one complee swiching cycle, he secondary winding peak curren (peak) can be expressed as follows: (peak) = I o ( ) 8Lf s, (1) where L=L 1 = = =L 4, is secondary volage of ransformer, and he volage sresses of free-wheeling diodes canbeexpressedasfollows: V r1 =V r =, V r3 =V r4 =, where is oupu volage. y applying he vol-second balance principle o he auxiliary inducors and oupu filer inducors, he volage gain of he proposed recifier hen can be derived as follows: () =, (3) where is duy raio of power swiches. From Figure 7 again, by using he inerleaved curren of he oupu inducors and L 4, he oupu curren ripple can be expressed: i o(ripple) = (1), (4) Lf s where f s is swiching frequency of power swiches. 4.. Performance of. From Figures 9 and 10, during one complee swiching cycle, he secondary winding peak curren (peak) canbeexpressedasfollows: (peak) =( n n )T L S ( n ) n 1 L, (5) where L=L 1 =, and he volage sresses of free-wheeling diodes can be expressed as follows: V r1 =V r = n, (6) where n=(n 1 n )/n 1 is urns raio of coupled inducors. y applying he vol-second balance principle o he auxiliary inducors and oupu filer inducors, he volage gain of he proposed recifier hen can be derived as follows: = n (1n). (7)

7 The Scienific World Journal 7 L 11 L 1 L 11 L 1 V o V o i L i L L 11 L 1 V o i L (c) Figure 11: Equivalen circui modes of he operaing over a half swiching cycle. Table 1: omparison beween N and. Volage gain Oupu curren ripple iode volage sress Peak curren of ransformer secondary winding N = i o(ripple) = (1 ) Lf s V r1 =V r = (peak) = I o ( )T L s = i o(ripple) = [ (1n) n(1 n) V r1 =V r = n ] Lf s (peak) =( n )T n L S ( n ) n 1 L From Figure 10 again, by combining he currens of and i L, oupu curren ripple can be deermined as i o(ripple) =[ (1n) ] Lf s. (8) To objecively judge he meris and demeris of N and, heir performances are compared as summarized in Table 1 and Figure 1, assuming ha he wo improved curren-doubler recifiers can be operaed wih idenical frequency, he same inpu and oupu volages, and load currens. 5. Experimenal esuls To veriy he performance of N and, wo ses of 500 W prooypes wih phase-shif full-bridge converers were buil (see Figures 13 and 14). The specificaions are lised as follows: (i) inpu volage V in :400V dc, (ii) oupu curren I o :4, (iii) oupu volage :1V dc.

8 8 The Scienific World Journal / i o(ripple ) /i o 0.5 N 5 Volage gain =80V =1V Oupu curren ripple (%) N =80V =1V uy raio uy raio 50 (peak) () Transformer peak curren N =80V =1V uy raio (c) Figure 1: Performance comparison beween N and : duy raio, oupu curren ripple, and (c) secondary peak curren of he ransformer. N 400 V dc Q 1 IFP Q 3 IFP450 b μf/50 V 7 μh T : 6 T IFP450 IFP450 Q Q r3 30PQ60 6 μh 6 μh N p N s L4 30PQ60 r4 L 1 6 μh 30PQ60 30PQ60 6 μh 1400 μf /5 V Vo Figure 13: Experimenal circui of he phase-shif full-bridge converer wih N.

9 The Scienific World Journal 9 n =6T n 1 =1T 400 V dc Q Q IFP450 3 IFP450 0T : 4T b L m = 1.6 mh μf/50 V 15 μh Q Q 4 4 IFP450 IFP450 L 11 =5μH 63PQ100 63PQ100 =5μH L 1 =0μH 31Q K/3 W 56 nf/100 V 56 nf/100 V 1.5 K/3 W 31Q06 =0μH o 1000 μf/ 5 V 1 V n =6T n 1 =1T Figure 14: Experimenal circui of he proposed phase-shif full-bridge converer wih. max = 0.3 max = 0.8 Figure 15: Measured waveforms of he secondary volage and curren of he ransformer: N and. il i L Figure 16: Measured waveforms of oupu filer inducor curren and i L : N and. (iv) oupu power P o :500W, (v) swiching frequency f s :100kHz. Figure 15 shows measured ransformer waveforms of N and under full load condiion. From hese measured waveforms, i can be seen ha N and can be exended duy raio. omparing beween N and, he N has a wide duy raio. Figure 16 shows waveforms of oupu filer inducors and L 4 for N and, from which i can be seen ha N has lower inducor curren ripple. Figure 17 shows waveforms of fullload oupu curren, from which i can be seen ha N has lower oupu curren ripple. Figure18 shows he comparison of efficiency measuremens beween N and, from

10 10 The Scienific World Journal i o = i L i o = i L Figure17:Measuredoupucurreni o waveforms: N and. Efficiency (%) Oupu curren () oupled curren-doubler recifier Noncoupled curren-doubler recifier Figure 18: Efficiency comparison beween N and associaed wih phase-shif full-bridge converers. which i can be seen ha can achieve higher efficiency a heavy load and can reach as high as 91%. The reason behind is ha N is used wih four inducors resuling in low conversion efficiency. 6. onclusions In his paper, he proposed phase-shif full-bridge converer wih N and under 500 W has been implemened. The N has he meris of exended duy raio, lower oupu curren ripple, and lower recifier diodes volage sresses, which can reduce he peak curren hrough he isolaion ransformer and swiches. However, in comparison beween efficiency of N and, he N has lower efficiency a full load condiion. The reason behind is ha N is used wih four inducors resuling in low conversion efficiency. For small size and high efficiency requiremens, is relaively suiable for high sep-down volage and high power conversion applicaions. onflic of Ineress The auhors declare ha here is no conflic of ineress regarding he publicaion of his paper. cknowledgmen This work was suppored by he Naional Science ouncil, Taiwan, under Gran no. NS10-1-E eferences [1] N. F. Zhang and J. Xu, novel PM boos PF converer wih fas dynamic response, IEEE Transacions on Indusrial Elecronics, vol. 58, no. 9, pp , 011. []L.Huber,Y.Jang,andM.M.Jovanović, Performance evaluaion of bridgeless PF boos recifiers, IEEE Transacions on Power Elecronics,vol.3,no.3,pp ,008. [3] J.-G. ho, J.. Sabaé, G. Hua, and F.. Lee, Zero-volage and zero-curren-swiching full bridge PWM converer for highpower applicaions, IEEE Transacions on Power Elecronics, vol. 11, no. 4, pp. 6 68, [4] M. Xu, J. Zhou, and F.. Lee, curren-ripler dc/dc converer, IEEE Transacions on Power Elecronics, vol.19,no.3,pp , 004. [5] Y. Jang, M. M. Jovanović, and Y.-M. hang, new ZVS-PWM full-bridge converer, IEEE Transacions on Power Elecronics, vol. 18, no. 5, pp , 003.

11 The Scienific World Journal 11 [6] X. uan and Y. Yan, n Improved phase-shifed zero-volage and zero-curren swiching PWM converer applied, in Proceedings of he 13h nnual pplied Power Elecronics onference and Exposiion (PE 98),vol.,pp ,February1998. [7] J.. bu-qahouq, H. Mao, and I. aarseh, New coupled-inducors curren-doubler opology, in Proceedings of he IEEE 34h nnual Power Elecronics Specialiss onference,vol.,pp , June 003. [8] L.Y.hang,K.H.hao,andT..hang, pplicaionofhigh volage raio and low ripple inerleaved - converer for a fuel cell, The Scienific World Journal, vol.01,riclei , 11 pages, 01. [9].-T. Tsai and.-l. Shen, High efficiency curren-doubler recifier wih low oupu curren ripple and high sep-down volage raio, IEEJ Transacions on Elecrical and Elecronic Engineering,vol.8,no.,pp ,013. [10].-T. Tsai and.-l. Shen, High sep-down inerleaved buck converer wih acive-clamp circuis for wind urbines, Energies,vol.5,no.1,pp ,01. [11] S.-Y. Tseng and.-t. Tsai, Phoovolaic power sysem wih an inerleaving boos converer for baery charger applicaions, Inernaional Journal of Phooenergy, vol. 01, ricle I , 15 pages, 01. [1].-T. Tsai and S.-H. hen, PV power-generaion sysem wih a phase-shif PWM echnique for high sep-up volage applicaions, Inernaional Journal of Phooenergy,vol.01,ricleI 83831, 11 pages, 01. [13] T.-F. Wu,.-T. Tsai, Y.-. hang, and Y.-M. hen, nalysis and implemenaion of an improved curren-doubler recifier wih coupled inducors, IEEE Transacions on Power Elecronics,vol. 3, no. 6, pp , 008.

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