Integrated Dual Output Buck Boost Conerter for Industral Applcaton. Dya enugopalan Electrcal and Electroncs Department Jyoth Engneerng College. Cheruthuruthy. Thrssur, Inda eshma aj C Electrcal and Electroncs Department. Jyoth Engneerng College, Cheruthuruthy. Thrssur, Inda Abstract Modern world s seekng for reduced sze, relable and less cost equpment Sngle Input Multple Output Conerters (SIMO) and the research on them are worthy. Ths s because there may be auxlary crcuts n addton wth the man power crcut. These auxlary crcuts and ICs work wth reduced oltage leel. The wde applcaton of SIMO conerters nclude telecommuncatons, ndustres, LED drers, hybrd electrc ehcles, dc based nano grds etc. The SIMO conerters exstng n the market faces some challenges because of ts crcut and cost. So research work s progresse under ths by the engneers. Integrated Dual Output Buck Boost Conerter s a Sngle Input Multple Output (SIMO) dc-dc conerter topology s one such research work to meet the challenges that hae been met by the conentonal SIMO dc to dc conerters.. It prodes one step-up and one step-down output whch can be acheed by replacng the swtch n conentonal boost conerter by two seres connected swtches. In conentonal SIMO topologes nddual dc-dc conerters are used for multple outputs whch requre about N swtches for N outputs that result n bulker crcuts. In the proposed topology, ths drawback s oercome by ncludng only N+ swtches for N outputs whch make the system smpler, relable and less cost. The selecton of boost conerter yelds a good effcency also. The analyss s smlar to conentonal buck and boost conerters that makes the control system much smpler and easer. The type of closed loop feedback system used n ths conerter ges a better cross regulaton and oltage regulatons whch are the common problems met by most of the SIMO dc-dc conerters. Most attracte feature s that ths conerter does not requre any other crcut components n order to achee good cross regulaton. The requrement of oltage regulators also s not needed wth ths conerter. These all agan reduces the cost of the product whch wll be an attracte feature n modern market. In order to check the behaor of the conerter smulaton s carred out n MATLAB enronment. The smulaton results aldate the operaton of the conerter. sources lke solar, wnd etc. Ths low power dstrbuton can be used for arous applcatons and the power s taken from the common bus. Here the oltage requrement for dfferent applcatons wll be dfferent Fg In ndustral feld the reducton n sze, relablty and less cost are attracte features whch lead to adanced research on SIMO dc to dc conerters. Ths s because arous ICs work on low oltages at dfferent low oltage leels. So SIMO dc to dc conerters hae ery good role n ndustral feld. The feld of power electroncs has a ery good role n desgnng a multoutput DC-DC conerter. Ths s because the power electronc conerters meet the requred power by utlzng less space. Moreoer wth proper PWM method the swtchng loss can be reduced. So that system effcency can be ncreased. Keywords DC-DC conerters, Integrated Dual Output Conerter (IDOC), Sngle Input Multple Output (SIMO). I. INTODUCTION Present day power electronc systems requre multple dc outputs at dfferent oltage leels. Ths s because auxlary crcuts are often present n addton to the man power stage, and they should be powered at low oltages. For example, such requrement of multple output can be seen n Hybrd electrc ehcles [3], dc based nano grds [], LED drers, standby power supples etc. For example DC based nano grd Fg.a a dc dstrbuton system generally met by local renewable energy Fg arous ndustral applcatons 63
In conentonal mult output dc-dc conerters nddual dc-dc conerters are used for dfferent outputs. Fg 3.a shows conentonal archtecture for sngle nput multple output dcdc conerters. Fg 3.a Fg 3.b Fg 3.a conentonal Fg 3.b proposed The followng secton dscusses the problems met by dfferent multple output dc-dc conerters. In some conentonal multoutput dc-dc conerters, nddual dc-dc conerters are used for output hang dfferent oltage requrement. An nddual dc-dc conerter s of two types, an solated dc-dc conerter and a non-solated dc-dc conerter. An solated dc-dc conerter requres at least two swtches at the front end, a transformer and at least two swtches at the back end. So four swtches, control dre crcutry and the transformer make the system more bulky and complex. For each and eery dc-dc conerter requre the aboe mentoned components. Hence the whole system becomes complex. In some solated mult output dc-dc conerter, secondary s nterleaed so as to get multple output. Hang the occurrence of more swtches and transformer, the power densty decreases. Moreoer the leakage nductance of the transformer decreases the effcency also. In some solated SIMO conerters, secondary wndngs are nterleaed for multple outputs [6]. The step up or step down outputs depend on the turns rato of the transformer. But n such conerters precse regulaton of each outputs s dffcult due to the magnetc couplng. For precse regulaton on each secondares addtonal lnear regulators, synchronous swtch post regulators etc are requred [], [4]. In specal connected two transformer (SCTTs) [6], to attan better cross regulaton at load condtons a Complementary Pulse Wdth Modulaton technque (CPWM) s used. So that t requres a bulky LLC resonant tank at the secondary, a snubber crcut to decrease the oltage stress of the rectfer. So that the system becomes bulky. In [7] a full brdge dual output dc-dc conerter, een f the LLC tank can be elmnated but each conerter share the common leg. In resonant based solated multple output conerters [8], due to the presence of nductance of the resonant tank there wll be cross regulaton problem. In order to reduce cross regulaton arous approaches such as magnetc couplng between seeral secondary wndngs, secondary sde post regulator ect should be ncluded.. Wth magnetc couplng, only the master output oltage can be regulated. Other slae outputs cannot be regulated. If Secondary Sde Post egulator SSP s connected t makes hgh cost of producton, bulky system, poor effcency and poor EMI performance. From the lterature dscussed aboe, generally most of the solated multple output dc-dc conerters are bulky, hae complex control system and less relable. A non-solated multple output dc-dc conerters are of two types, DC-DC conerters wth cascaded dc-dc stages [4], [9] or tme-multplexed and current- channelzed multple-output conerters. In conerters wth cascaded dc-dc stages, the mpedance nteracton between nddually desgned conerters may make the cascaded system unstable. To attan stablty crcuts such as adapte acte capactor conerter crcuts should be connected. The presence of capactance and nductance n such crcuts make poor oltage regulaton. Moreoer t needs to desgn separate dc bus oltage controller and unbalanced loads can nduce lowfrequency oscllatons on the current of the sources. In tme multplexed and current channelzed multple output conerters, practcally t becomes more dffcult to generate swtchng functons that can share a fxed swtchng perod. So the control system of the conerters s ery complcated. Hence the whole system becomes unrelable. A multple output conerter has to meet many challenges. They are ts ablty to regulate each of the nddual outputs precsely, to hae better cross-regulaton behaour due to changes n the other output and to dese a sutable control system to coordnate the power flow between the dfferent outputs. For a multple output conerter, cross regulaton [6], [3], [8] s the change n oltage on one output (expressed as a percent) caused by the load change on another output. Ths may be due to conducton loss of dodes, magnetc wndngs of the transformer, ES of the capactor, external nductors ncluded n the crcut. Cross regulaton problems leads to the use of addtonal lnear and non-lnear swtchng. But n ths conerter a better closed loop feedback control system s employed for the reducton of cross regulaton. In order to mtgate the aboe problems assocated wth SIMO conerter a new erson hang an ntegrated archtecture wth a step up output and multple step down outputs t replaces all the nddual dc-dc conerters be a seres connected swtches n a conentonal boost crcut. The ntegrated multple-output conerters (IMOCs) Fg.b n ths paper, utlze a reduced number of swtches ((N + ) swtches for N outputs) compared wth separate conerters. In conentonal conerters wth separate dc-dc conerters N swtches are requred. The use of a lower number of swtches reduces the cost of the swtch and ts assocated drers. In addton, due to ts ntegrated archtecture, all the outputs of the system are regulated usng the same set of swtches, and hence, the coordnaton control s easer. The crcut analyss and the control system requrement are exactly smlar to that of conentonal buck and boost conerters. But compared wth conentonal buck or buck- 63
boost conerter, the nput flter requrement s lower as the nput and output current of ths proposed conerter are lnear. By the mplantaton of proper feedback control system whch wll be dscussed n the followng secton, the regulaton of outputs can be done nddually. Hence good oltage regulaton and cross regulaton can be acheed. The cross regulaton agan can be decreased by replacng the dode by a swtch. The swtchng pattern of ths swtch s just the complementary of the second swtch n Integrated Dual Output Buck Boost Conerter. Ths paper s organzed as follows: Ths paper studes the ntegrated dual-output conerter (IDOC), whch has two dc outputs a step-up and a step-down. Proposed topology crcut and extended erson crcut are dscussed n secton II. The analyss of proposed topology and desgn of passe components are dscussed n secton III. The smulaton of proposed topology wth D =0.33 and D =0.33 s shown n secton I. Cross regulaton reducton and oltage regulaton are shown n that secton. Secton concludes the paper. II. POPOSED TOPOLOGY A. Crcut dagram In the proposed topology the swtch n the conentonal boost conerter s replaced by two seres swtches. For Integrated Dual output Buck Boost conerter two swtches S and S whch are two Mosfets. L, L are two nductors, C and C are two capactors. Fg 4 Proposed topology For outputs greater than two can be formed by connectng a seres of swtches as shown n the Fg 5. There are N+ swtches for N outputs whch ge one step up output and multple step down outputs. Fg 5 Integrated mult output dc-dc conerter. III. ANALYSIS OF POPOSED TOPOLOGY The Integrated Dual Output Buck boost conerter s deeloped usng two bdrectonal swtches S and S. These are connected n seres n a conentonal boost crcut. There are three dstnct modes of operatons whch are dscussed n the followng sectons. A. Swtchng nterals Interal - Both swtches S and S On When both swtches are turned on, the dode D wll be reerse based and that crcut wll be open crcuted. The nput current flows through L, S and S. The nductor current bulds up to ts maxmum alue. Whle L dscharges the charge that was stored n the preous mode. Ths mode of operaton s defned by duty rato D. C C n Interal - S s On and S s Off When S s on and S s off, the nductor dscharges and the nductor current s dstrbuted nto two components. One D s flowng through dode D, and the other porton whch bulds as n conentonal buck conerter. The step-down conerter draws energy from the source durng ths nteral. The dode current D s equal to the dfference between the nductor currents and. The tme duraton for mode operaton s defned to hae a duty cycle of D. C n C Interal- 3 S s off S s on When S s off and S s on, the nductor L dscharges through the antparallel dode of swtch S. Ths nteral s smlar to the freewheel perod of conentonal buck conerter. The nductor L dscharges anl falls to a mnmum alue. The dode current D and are smlar n ths mode. Hence durng ths nteral, both nductors L and L ge out ther energy to ther respecte outputs. C C n 633
The swtchng strategy makes the conerter operate n the nteral sequence (III), (II), (I), (II), (III) durng each perod. B. Steady state behaour andd, nstead of only one duty cycle as n the case of a buck conerter. Smlarly, the step-up gan ares between ) oltage gan For nductor L, n D Solng, n * D ( n )*( D ) 0 n ( D ) Ths s the expresson for the conentonal boost conerter. So yelds step up output oltage. () () Thus, the Integrated Dual Output Buck Boost Conerter preseres the qualtes of both buck and boost conerters n an ntegrated archtecture. C. Desgn of passe components Desgn of passe components n ths conerter s same as that of the conentonal buck and boost conerters..inductance L For nductor L, (3) )* D ( D ) 0 ( Solng, Substtutng () n (4), D D D ) ( (4) (5) Assume 35% current rpple. Capactor C Assume 3% rpple. Inductor L D ( D ) C f sw D T s (6) (7) )ange of nput oltage Because both duty cycle D and D share the same swtchng perod, duty cycles D and D should satsfy D + D. L Assume 35% rpple ( D ) f sw (8) For any partcular alue of the duty cycle D, the step-down gan ares wthn the range 0 n Ths conerter can prode step-down output ranges aryng from zero to the nput oltage. Compared wth a conentonal buck conerter, the IDOC can prode wde step-down outputs at acceptable duty ratos of swtches. Ths s because the step down output depends upon both D Capactor C C Assume 3% rpple ( DT 8L s (9) 634
TABLE I. DESIGN SPECIFICATION Sl No Parameter attrbutes Input oltage n Output oltage 8 3 Output oltage 6 4 Step up dc load I 5A 5 Step down dc load I 5A 6 Swtchng frequency 00kHz TABLE IIDESIGN ALUES OF PASSIE COMPONENTS Wth D =0.33 and `D=0.33 obtaned both step up outputoltage of 7.6 and step down output of 6. The load resstance used are =5Ω and =3Ω.The nductor currents are also obtaned. A ) oltage egulaton cross regulaton In order to check the effect of sudden change n any of the outputs, two step loads are appled. In the frst case a step load of 0 to A and n the second case a step load of 0 to 5A as loads n the step down crcut. The duty cycles D and D are taken as 0.33. Sl No Components attrbutes Inductor L 5μH Inductor L 0μH 3 Capactor C 500μF 4 Capactor C 00μF I CLOSED LOOP SIMULATION A closed loop feedback control system s mplemented n ths conerter to prode better cross regulaton whch s already explaned n the aboe secton. The subsectons of ths secton refers the smulated waeforms at D=0.33 and D=0.33. A Waeforms ) When D =0.33 and D =0.33 Fg 7.a Fg 7.b Fg 6 Cross egulaton a). step load of 0 to A b). step load of 0 to 5A When both the step load changes were appled, the step up output and the step down output remaned constant. At no load, there were more rpples than at the loaded condton. But the aerage alue remaned as the reference alues.. Fg 6 B Step change n the reference In order to check the performance of the conerter a step change of 4 to 6 s appled as the reference n the control crcut. 635
Fg 8 Step change of 4 to 6 n the reference of step down oltage Fg 9.a When the reference oltage at the step down crcut s changed from 4 to 6, the step up oltage remaned constant at 8. There was a step change n (4 to 6) as per the reference gen. The below table show the range of step up and step down outputs that can be obtaned wth conerter. It also ge an dea about the faorable alue of duty cycles. The same smulaton s done wth the step change n the ref and the data s gen n the table I. TABLE III Table D s kept constant at 0.33 D 0.39 7.65 0.67 7.64 0. 7.69 0.33 7.7 0.389 7.64 0.444 7.54 TABLE I D IS KEPT CONSTANT AT 0.33 D The range of step down output oltage s larger than the step up output oltage. From the table t s understood that the conerter ges a better perfomance at D =0.33 and D =0.33. 3) Lne regulaton 0.43 5.78 0.333 5.8 0.36 5.59 In order to check the lne regulaton, 0% ncrease and decrease of nput oltage s appled as step oltages Fg 9.b Fg 9 Lne egulaton a) 0% decrease b). 0% ncrease In both the cases the output oltage remaned same as n the case of n=. A ± 5% lne regulaton lmt s obtaned by the smulaton. The crcut can be modfed by replacng the dode by a controllable swtch for attanng a wde range of step up loads. It can work een at zero loads at the step up crcut. The control sgnal appled to ths swtch wll be the complementary of swtch S. The smulaton s done wth duty cycles D =0.33 and D =0.33. From the smulaton result whch s shown n Fg 9 s satsfactory. The output oltages s reached up to 7.6 and reached up to 5.8. From Fg the no load operaton can possble for the boost crcut. remaned at 7.6 whle was 0A. Ths shows the better cross regulaton property een under the no load condton n the boost crcut. 636
4) Effcency calculaton Power output for step up output= *I=6.8W Power output for step down output=*i=.53w Power consumed by the swtch S3=0.3W Power nput=n*in=7.7w Power output=80.83w Effcency=(6.8+.53)/80.83=89.95% Fg 0 Modfed topology CONCLUSION Ths paper has proposed an ntegrated dual output buck boost dc-dc conerter wth smultaneous step-up and stepdown outputs. Ths topology can be extended for N outputs wth one step up output and multple step-down outputs. In contrast wth conentonal N output dc-dc conerter, t requres only N+ swtch whch reduces the cost and complexty. It has wder step-up oltage range and a better cross regulaton. Two outputs can be separately regulated usng a proper feedback control system. The cross regulaton s well mproed by ths topology whch could be llustrated by the smulaton. The lne regulaton also could be erfed by the smulaton and that gae a ±5% of nput oltage. The extended erson ges the no load operaton for the step up output crcut. Ths shows a better cross regulaton and oltage regulaton. The conerter ges an effcency of 89.95%. The conerter behaor has been erfed usng the software MATLAB and the smulaton results aldate the behaor of the conerter. EFEENCES Fg Current and oltage across S 3= From the smulaton the nserton of addtonal swtch consumes only 0.3W. Fg No load operaton at the step up crcut that shows a better cross regulaton. [] C. N. Onwuchekwa and A. Kwasnsk, A modfed-tme-sharng swtchng technque for multple-nput DC DC conerters, IEEE Trans. Power Electron., ol. 7, no., pp. 449 45, No.. []. Adda, O. ay, S. Mshra, and A. Josh, Synchronous reference frame based control of swtched boost nerter for standalone DC nanogrd applcatons, IEEE Trans. Power Electron., ol. 8, no. 3, pp. 9 33, Mar. 3. [3] A topologcal Ealuaton of solated DC/DC conerters for auxlary power modules n electrfed ehcle applcaton. uoyu Hou, Berker Blgn, Al Emad,IEEE 5. [4] P. Shams and B. Fahm, Dynamc behaor of multport power electronc nterface under source/load dsturbances, IEEE Trans. Ind. Electron., ol. 60, no. 0, pp. 4500 45, Oct. 3 [5] A.. Stankoc, L. Nerone, and P. Kulkarn, Modfed synchronousbuck conerter for a dmmable HID electroncs ballast, IEEE Trans. Ind. Electron., ol. 59, no. 4, pp. 85 84, Apr.. [6] Modellng of cross regulaton n conerters contang coupled nductors Dragon Maksmoc, obert Ercson, Carl Gresbach.IEEE APEC, CA Feb. 998 [7] J.-K. Km, S.-W. Cho, C.-E. Km, and G.-W. Moon, A new standby structure usng mult-output full-brdge conerter ntegratng flyback conerter, IEEE Trans. Ind. Electron., ol. 58, no. 0, pp. 4763 4767, Oct.. [8] M. odrguez, G. Stahl, L. Corradn, and D. Maksmoc, Smart DC power management system based on software-confgurable power modules, IEEE Trans. Power Electron., ol. 8, no. 4, pp. 57 586, Apr. 3. [9] Mnmsed trancent and steady-state cross regulaton n 55 nm CMOS sngle nductor Dual-ouput (SIDO) step down DC-DC conerter. Yu- Hueo Lee. Tzu-Ch IEEE. [0] Impact of multplexng on the dynamc requrements of Analog to dgtal conerters. Tm J Soberng IEEE996 [] Photooltac based hgh effcency SIMO Dc to DC conerter. J. Kpndalaah,I. ahul 4 637
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