5h Inernaional Conference on Environmen, Maerials, Chemisry and Power Elecronics (EMCPE 016 Pulse Train Conrolled PCCM Buck-Boos Converer Ming Qina, Fangfang ib School of Elecrical Engineering, Zhengzhou Universiy, Zhengzhou 450001, China a qinming@zzu.edu.cn, b13603714813@163.com Keywords: pulse rain (PT conrol, pseudo coninuous conducion mode (PCCM, Buck-Boos converer, conrol scheme. Absrac. In order o reduce he impac of he decrease of inducor curren during he freewheel swich on he pulse of nex cycle, his paper pus forward a novel conrol scheme of pulse rain (PT according o he working characer of he pseudo coninuous conducion mode (PCCM Buck-Boos converer. The novel scheme conains wo pseudo coninuous variables and makes he conroller produce differen curren-conrolled pulses depending on differen-energy volage-conrolled pulses. The working process of he PCCM Buck-Boos converer under his new conrol scheme is analyzed in deail and he raio of high-energy and low-energy volage-conrolled pulses is presen. Compared wih radiional conrol scheme wih one pseudo coninuous variable, he performance of he new converer is improved significanly. Simulaion and experimenal resuls verify he feasibiliy of he new conrol scheme and he correcness of he heoreical analysis. 1. Inroducion Wih he wide applicaion of swiching power supply, he requiremen of is performance is increasing [1]. The conrol echnology of swiching power supply is he main facor ha affecs is performance. The pulse widh modulaion (PWM echnique based on linear conrol heory has gained increasing aenion in recen years because of is poor ransien characerisics and robusness and difficul design of compensaion nework []. People have been rying o use beer conrol echnology o improve he performance of swiching power supply o mee he requiremens of elecronic devices [3, 4]. Pulse rain (PT conrol echnology proposed in recen years is a new nonlinear conrol echnology of swiching power supply [5]. I has been widely sudied because of is simple conrol circui and good ransien characerisics and robusness. PT conrol echnique prese high-energy and low-energy volage-conrolled pulses which have he same frequency and differen duy raio. Selec suiable pulse as he effecive conrol pulse hrough he relaionship beween he oupu volage a he iniial ime of swiching cycle and he erence volage. Some high-energy and low-energy volage-conrolled pulses form a pulse rain cycle and he conroller adjuss he oupu volage by adjusing he combinaion of he wo pulses in pulse rain cycle. The swiching converer operaing a a consan frequency can work in disconinuous conducion mode (CM or coninuous conducion mode (CCM. A presen, he research of PT conrol echnology is mosly based on he CM converer, whose abiliy of carrying capaciy is poor. Pseudo coninuous conducion mode (PCCM is a special operaing mode differen from CM and CCM [6]. A any ime he inducor curren is greaer han zero, and he inducor curren is kep consan raher han zero before he end of he swiching cycle. Considering he equivalen series resisance of inducor and capacior, his paper pus forward a new pulse rain conrol sraegy, which makes he Buck-Boos converer work in PCCM mode. The conrol process and high-energy and low-energy volage-conrolled pulses are analyzed. Finally, he feasibiliy of he mehod and he correcness of he heoreical analysis are verified by simulaion and experimen. 016. The auhors - Published by Alanis Press 404
. PT Conrolled PCCM Buck-Boos Converer Fig. 1 shows he circui srucure diagram of PT conrolled PCCM Buck-Boos converer. The diode and he swich S are in parallel wih he inducor, which could provide a coninued flow pah for curren. Converer can work in PCCM hrough conrolling he on-off of he wo swiches. There are hree pars in each swiching cycle of a PCCM Buck-Boos converer. When he swich S 1 is on and S is off, he inducor curren i and he oupu volage V o ramp up. When S 1 and S are off, i ramps up and. When S 1 is off and S is on, i says he same and V o ramps down. S 1 S 1 + V i i C R V o V p1 V p - rive circui Conroller i <I V o <V V o V Fig. 1 The circui srucure diagram of PT conrolled PCCM Buck-Boos converer Acually, he inducor curren will be linearly decreased due o he loss of he inducance and he swich. Considering his losses, his paper proposes a new conrol sraegy of PT o make he Buck-Boos converer work in PCCM, which has wo pseudo coninuous variables. The conroller is composed of a pulse rain conroller and a pseudo coninuous conroller. In he beginning of each swiching cycle, V o is compared wih he erence volage V. When V o is lower han V, pulse rain conroller generaes high-energy volage-conrolled pulse P 1 o conrol S 1. When i drops o he erence curren I, he pseudo coninuous conroller generaes he curren-conrolled pulse P o make S urn on, hen i freewheels hrough S and unil he nex swiching cycle begins. When V o is higher han V, he pulse rain conroller generaes low-energy volage-conrolled pulse P 1 o conrol S 1. When his cycle has worked for a cerain period of ime, he pseudo coninuous conroller generaes he curren-conrolled pulse P o make S urn on, which is differen from he period of P 1, hen i freewheels hrough S and unil he nex swiching cycle begins. Fig. shows he conrol flow char of his novel conrol scheme. There is only one pseudo coninuous variable I in radiional PCCM converer. Wheher he pulse rain conroller produces P 1 or P 1, he pseudo coninuous conroller will produce corresponding curren-conrolled pulse o conrol he conducion of S when i drops o I. Bu in pracice, for he ime of freewheel swich of P 1 is long, he inducor curren drops a lo, which will seriously affec he nex cycle. For he ime of freewheel swich of P 1 is shor, he inducor curren drops can be ignored. The inducor curren waveforms of hese wo cases are shown in Fig. 3. The novel conrol sraegy adds one ime conrol volume on he basis of a erence curren, which can affec nex cycle when he pulse rain conroller produces P 1 and he conrol performance can be improved significanly. Fig. 4 shows he main waveforms of his PT conrolled Buck-Boos PCCM converer wih wo pseudo coninuous variables. 405
Clk eec V o V o < V? N Y V p1 P V p1 P Turn S off Turn S off N i I?? Y Y Turn S off Fig. The conrol flow char N i I (a Ideal waveform i I (b Acual waveform Fig. 3 Inducor curren waveforms wih one pseudo coninuous variable v cl k i I S 1 T S T T V V o i S1 Fig. 4 Main waveforms wih wo pseudo coninuous variables 3. igh-energy and ow-energy Volage-conrolled Pulses For he PT conrolled PCCM Buck-Boos converer, during he swich cycle of P 1, he conducion ime of S 1 is T, he waveform of which is shown in Fig. 4. The mean value of he curren flowing hrough he S1 during he swiching period is TVi I = I, (1 S 1 + where is he inducance of converer. The inpu erminal curren of he converer is he curren ha flows hrough S 1, so he energy obained from he inpu during he swiching cycle P 1 is 406
( Vi T E i = ViI T +. ( Similarly, he energy obained from he inpu during he swiching cycle P 1 is ( Vi T E i = ViI T +. (3 Assuming he pulse rain cycle is composed of μ high-energy volage-conrolled pulses and μ low-energy volage-conrolled pulses when he converer is sable. The oal energy of he converer obained from he inpu of he pulse rain cycle is E i = E i + E i. (4 Assuming he load power of he converer is P and he conversion efficiency of energy is η. There is he following relaionship η E i = P ( + T. (5 By equaion (4 and equaion (5, we obain P 1 V I = [ η i ( + + Vi Tη( + ]. (6 ( + The equaion (6 shows he main circui parameers and he conrol parameers of he converer and he quaniaive relaion of high-energy and low-energy volage-conrolled pulses in he pulse rain cycle, which can be used as erence in he design of conrol sysem. According o he analysis mehod of PCCM converer, we can obain he load power of pulse rain cycle in CM, ha is Vi Tη( + P =. (7 ( + By comparing equaion (6 and equaion (7, we know ha he load power of he PCCM is higher han ha of he CM under he same parameers of converer. We can ge he quaniy proporion beween P 1 and P 1 of pulse rain cycle of he PCCM. The equaion is P ηvii ηvi T =. (8 ηvii + ηvi T P Similarly, we can ge he quaniy proporion beween P 1 and P 1 of PT conrolled CM converer from equaion (7. The equaion is P ηvi T =. (9 η Vi T P From equaion (8 and (9, we can draw he following conclusions. If he inpu volage is consan while he load power is increased, he number of P 1 in pulse rain conroller would relaively increase. If he load power is consan and he inpu volage rises, pulse rain conroller would generae more P 1. We can draw he relaion curve beween μ /μ and P of PT conrolled PCCM Buck-Boos converer and PT conrolled CM Buck-Boos converer from equaion (8 and (9, which is shown in Fig. 5. Where, V i =10V, V o =9V, P=1.8W, T=50μS, =100μ, C=470μF, =0.1, =0.4 and I =0.5A. μ/μ 5 4 3 1 0 CM PCCM 1 P/W 3 4 Fig. 5 Relaion curve beween μ /μ and P 407
Fig. 5 shows ha μ /μ increases wih he increase of P. When P is increased o a cerain value, μ /μ increases rapidly and he converer can work normally. The range of load power of PCCM is greaer han CM. I can be concluded ha, PCCM converer improves he load capaciy compared wih CM converer. 4. Simulaion Research In order o prove he correcness of he heoreical analysis, he PT conrolled PCCM Buck-Boos converer wih wo pseudo coninuous variables is simulaed, whose circui parameers and conrol parameers are he same wih he las secion. Fig. 6 shows he simulaion waveforms of volage-conrol pulses of he PCCM converer under he same inpu volage and differen load power. When P is 1.8W, he pulse rain cycle is P 1 -P 1 -P 1 -P 1 -P 1, μ /μ =/3. When P is 1.W, he pulse rain cycle is P 1 -P 1 -P 1 -P 1, μ /μ =1/3. When P is 1.W, he pulse rain cycle is P 1 -P 1 -P 1 -P 1, μ /μ =3. Vp1 Vp1 Vp1 (ap is 1.8W (bp is 1.4W (cp is 3.4W Fig. 6 Simulaion waveforms The simulaion resuls show ha he pulse rain conroller generaes more low-energy volage-conrolled pulses when he load power is ligh and he pulse rain conroller generaes more high-energy volage-conrolled pulses when he load power is heavy. In addiion, PT conrolled Buck-Boos CM converer can work properly when P is 3.4W, which indicaes ha he PCCM converer can improve he load carrying capaciy compared o CM converer. The simulaion resuls verify he correcness of he heoreical analysis. 5. Experimenal Verificaion In order o verify he feasibiliy of he new conrol sraegy and he correcness of he heoreical analysis and simulaion research, his paper build he experimen plaform o es he PT conrolled PCCM Buck-Boos converer wih wo pseudo coninuous variables, whose experimenal parameers are he same wih simulaion parameers. Swiches use IRF305. iodes use SR560. Comparaors use M393. Phooelecric couplers use 6N137. Conroller uses digial conroller FPGA, whose model is EP4CE15F17C8. rivers use A310. Fig. 7 shows he experimenal waveforms of volage-conrolled pulses and inducor curren when he load power of he PCCM converer is 1.8W, 1.W and 3.4W, respecively. The pulse rain cycle is P 1 -P 1 -P 1 -P 1 -P 1, P 1 -P 1 -P 1 -P 1 and P 1 -P 1 -P 1 -P 1, respecively. 408
Vp1(1V/div i(0.5a/div V p1 i i(0.5a/div Vp1(1V/div V p1 i (50μs/div (50μs/div (a P is 1.8W (b P is 1.W V p1 i(0.5a/div Vp1(1V/div i (50μs/div (cp is 3.4W Fig. 7 experimenal waveforms The experimenal resuls are in agreemen wih he heoreical analysis and simulaion resuls. The high-energy volage-conrolled pulse generaed by he conroller is relaively increased wih he increase of load power and decline wih he decrease of load power. The experimenal resuls verify he feasibiliy of he new conrol scheme and he correcness of heoreical analysis and simulaion research. 6. Summary Tradiional PT conrolled PCCM converer has only one pseudo coninuous variable. Based on his, his paper proposes a novel PT conrolled sraegy wih wo pseudo coninuous variables. The conroller generaes corresponding curren-conrolled pulses according o he volage-conrolled pulses, which makes he performance of he converer improved significanly. The working process of he converer is analyzed in deail. The operaion sae and pulse combinaion of PT conrolled Buck-Boos PCCM converer is analyzed hrough he simulaion and experimenal research. The feasibiliy of he new conrol mehod and he correcness of he heoreical analysis are verified. A he same ime, i is proved ha he load carrying capaciy of PT conrolled PCCM converer is significanly improved compared wih he PT conrolled CM converer. Acknowledgmens This research is financially suppored by he Naional Naural Science Foundaion (510714 of China and China Posdocoral Science Foundaion (01M51408. 409
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