A Systematic Approach to Synthesizing Multi-Input DC–DC Converters.pdf

116 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 24, NO. 1, JANUARY 2009

A Systematic Approach to SynthesizingMulti-Input DC–DC Converters

Yuan-Chuan Liu and Yaow-Ming Chen, Senior Member, IEEE

Abstract—The objective of this paper is to propose a general ap-proach for developing multi-input converters (MICs). The derivedMICs can deliver power from all of the input sources to the load ei-ther individually or simultaneously. By analyzing the topologies ofthe six basic pulsewidth modulation (PWM) converters, the methodfor synthesizing an MIC is inspired by adding an extra pulsatingvoltage or current source to a PWM converter with appropriateconnection. As a result, the pulsating voltage source cells (PVSCs)and the pulsating current source cells (PCSCs) are proposed forderiving MICs. According to the presented synthesizing rules, twofamilies of MICs, including quasi-MICs and duplicated MICs, aregenerated by introducing the PVSCs and the PCSCs into the sixbasic PWM converters.

Index Terms—Multi-input converter, pulsating source,pulsewidth modulation, renewable energy.

I. INTRODUCTION

BASICALLY, a pulsewidth modulation (PWM) convertercan be used to draw power from an energy source [1]–[9].

In order to combine more than one energy source, such as thesolar array, wind turbine, fuel cell, and commercial ac line,to get the regulated output voltage, different circuit topolo-gies of multi-input converters (MICs) have been proposed inrecent years. These MICs are used in the applications of photo-voltaic (PV)–wind power system [10]–[12], PV–utility system[13]–[17], hybrid vehicle [18]–[22], and others [23]–[26]. Dif-ferent PWM converters can be put in series to implement theMIC and the regulated output voltage can be achieved [10]–[12].Such an MIC can continue to operate even if one of the dcsources has failed. Another approach is to put PWM convertersin parallel without electrical isolation or with electrical isolationby using the coupled transformer [13]–[17], [23], [24]. Controlschemes for these MICs with paralleled dc sources are based onthe time-sharing concept because of the clamped voltage. Hence,only one of the dc sources is allowed to transfer power to the loadat a time, i.e., power of different dc sources cannot be transferredto the load simultaneously. In addition, various MICs, includingthe one proposed by the author, were developed with no expla-nation as to how they were generated [18]–[22], [25], [26].

The objective of this paper is to propose a systematic approachto unify the generation of MIC topologies excluding the onesthat contain coupled transformers. Based on this approach, some

Manuscript received March 20, 2007; revised February 26, 2008. Currentversion published February 6, 2009. This paper was presented at the 38thIEEE Power Electronics Specialist Conference (PESC 2007), Orlando, FL,June 17–21. Recommended for publication by Associate Editor J. Cobos.

Y.-C. Liu is with AcBel Polytech, Inc., Taipei 251, Taiwan (e-mail:[email protected]).

Y.-M. Chen is with the Department of Electrical Engineering, National TaiwanUniversity, Taipei 10617, Taiwan (e-mail: [email protected]).

Digital Object Identifier 10.1109/TPEL.2008.2009170

Fig. 1. General form of the MIC.

of the existing MIC topologies and numerous new ones can begenerated systematically.

The general form of an MIC consists of several input sourcesand a single load, as conceptually shown in Fig. 1. Each of theinput-to-output port pair can be regarded as an individual PWMconverter separately. In general, all of the input sources candeliver power to the load either individually or simultaneouslythrough the MIC. When only one of the input sources feedsthe MIC, it will transfer power to the load individually and theMIC will operate as does a PWM converter. On the other hand,when more than one input sources are supplied to the MIC, allthese input sources will deliver power to the load simultaneouslywithout disturbing each other’s operation. Moreover, no poweris transferred from one of the input sources to another. The MICsdeveloped in this paper can save the amount of inductors and/orcapacitors as compared to the ones obtained by simply paral-leling the outputs of the converters. In addition, for the energysources with intermittent properties such as the PV array and thewind turbine, the proposed MICs can achieve higher converterutilization. For simplicity and convenience, the MICs devel-oped and discussed in this paper are limited to two-input-sourceMICs. In fact, the MICs with more than two input sources canalso be synthesized by the same principle presented in this paper.

In this paper, the topologies of the six basic PWM converterswill be reviewed first, from which the method for synthesizingMICs is derived [27], [28]. Two basic circuits, the pulsatingvoltage source cell (PVSC) and the pulsating current sourcecell (PCSC), will be defined as the building cells and usedto generate MICs. Then, the principle of synthesizing MICswill be addressed and two families of MICs will eventually besynthesized. Finally, a brief discussion on the developed MICswill be presented.

II. BRIEF REVIEW OF BASIC PWM CONVERTER TOPOLOGIES

The six basic PWM converters, which include buck, boost,buck–boost, Cuk, zeta, and single-ended primary inductance

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LIU AND CHEN: SYSTEMATIC APPROACH TO SYNTHESIZING MULTI-INPUT DC–DC CONVERTERS 117

Fig. 2. Three portions of a basic PWM converter.

Fig. 3. Topological structures of the six basic PWM converters. (a) Buckconverter. (b) Boost converter. (c) Buck–boost converter. (d) Cuk converter.(e) Zeta converter. (f) SEPIC converter.

converter (SEPIC) are widely utilized in power electronics ap-plications. Topologically, each basic PWM converter can bedivided into two or three portions, namely input portion (IP),energy buffer portion (EBP), and output portion (OP), as shownin Fig. 2, where the buck and the boost converters have noenergy buffer portions. Topological structures of the six basicPWM converters are shown in Fig. 3 with input portions, energybuffer portions, and output portions marked. In the energy bufferportion, the inductor and capacitor are employed to play the roleof energy buffers. Within a switching cycle of the switch in theinput portion, the inductors and/or the capacitors draw and storeenergy from the input portion at one moment and then deliverthe stored energy to the output portion at another moment with-out consuming any energy. In this process, each inductor carriesa nonzero dc current and each capacitor carries a nonzero dcvoltage. Thus, an inductor and a capacitor can be considered asa current buffer and a voltage buffer, respectively. For readilydescribing the PWM converter topologies, the rectangular com-ponents shown in Fig. 3 are used to denote either the currentbuffer or the voltage buffer.

In the input portion, the voltage source or the current sourceis chopped into a high-frequency pulse-train voltage or currentwaveform by the switch. When this high-frequency pulse-trainvoltage or current waveform feeds to the output portion, it willbe filtered out to be a dc current or voltage by the current-typeor voltage-type output portion. When the high-frequency pulse-train voltage waveform is connected to a current buffer, it will beconverted into a high-frequency pulse-train current waveform

Fig. 4. Circuit configuration of the PVSC. (a) Conceptual diagram of thePVSC. (b) Buck-type PVSC. (c) Cuk-type PVSC. (d) Zeta-type PVSC.

Fig. 5. Circuit configuration of the PCSC. (a) Conceptual diagram of thePCSC. (b) Boost-type PCSC. (c) Buck–boost-type PCSC. (d) SEPIC-typePCSC.

Fig. 6. Feasible circuit configuration of a PVSC connecting to a prime PWMconverter. (a) Energy buffer portion connection. (b) Output portion connection.

Fig. 7. Feasible circuit configuration of a PCSC connecting to a prime PWMconverter. (a) Energy buffer portion connection. (b) Output portion connection.

through the current buffer. Similarly, the high-frequency pulse-train current waveform will be converted into a high-frequencypulse-train voltage waveform through the voltage buffer. Finally,either the high-frequency pulse-train voltage waveform or cur-rent waveform will be filtered out to be a dc current or voltageby the current-type or voltage-type output portion.



Fig. 8. Illustration of the MIC derived from the buck-type PVSC and the zeta converter. (a) Buck-type PVSC and the zeta prime converter. (b) PVSC is insertedinto the output sink of the prime converter. (c) Synthesized MIC with appropriate circuit configuration. (d) PVSC is inserted into the current buffer of the primeconverter. (e) Synthesized MIC with appropriate circuit configuration.

III. CONFIGURATION OF PVSCS AND PCSCS

As described previously, the output portion of the PWMconverters sees a high-frequency pulse-train voltage or currentwaveform from the input portion or the energy buffer portion.By filtering out this high-frequency pulse-train voltage or cur-rent waveform with the output portion, a dc voltage or currentcan be obtained. From this viewpoint of circuit topology, themethod for synthesizing an MIC can be inspired by adding anextra pulsating voltage source or current source to a conventionalPWM converter with appropriate connection. In this section, thePVSC and the PCSC, which are formed by a pulsating voltagesource along with a diode and a pulsating current source alongwith a diode, are defined. The principle of synthesizing MICs bycombining the PVSCs or the PCSCs with the PWM converterswill be addressed in the next section.

A. Configuration of PVSCs

In Fig. 4, the pulsating voltage source as well as the paralleldiode are lumped together and named PVSC. When a PVSCis introduced into a PWM converter to yield an MIC, it cannotbe connected in parallel with any branch of the PWM con-verter; otherwise, the voltage across the connected branch willbe clamped by the introduced PVSC. Hence, a PVSC can be

connected only in series with one of the branches of a PWMconverter for developing an MIC. In this circuit configuration,the parallel diode in the PVSC is supplemented for circulat-ing the possible current difference between the pulsating volt-age source and the connected branch of the PWM converter.According to the topological properties of PWM converters,the pulsating voltage source can be generated by a dc voltagesource in series with a switch, a dc current source in parallelwith a switch followed by a capacitor, or a dc voltage sourcein series with a switch followed by an inductor and a capaci-tor in sequence. Thus, the feasible circuit configurations of thePVSC can be drawn in Fig. 4(b)–(d), and are named buck-type,Cuk-type, and zeta-type PVSCs, respectively.

B. Configuration of PCSCs

The conceptual circuit configuration of the PCSC is depictedin Fig. 5(a), where it consists of a pulsating current source inseries with a diode. The only eligible method to insert a PCSCinto a PWM converter to develop an MIC is to connect a PCSCin parallel with one of the branches of the PWM converter. Thisis because the current through the connected branch will beclamped by the pulsating current source if the PCSC is in seriesconnection. The series diode in the PCSC functions to blockthe possible voltage difference between the voltages imposed



Fig. 9. MICs synthesized by the buck-type PVSC with different primeconverters. (a) Buck converter. (b) Buck–boost converter. (c) Cuk converter.(d) Zeta converter. (e) SEPIC converter.

on the pulsating current source and the connected branch ofthe PWM converter. Similar to the generation of the pulsatingvoltage sources, the pulsating current sources can be generatedaccording to the topological properties of the PWM converters,from which the feasible circuit configurations of the PCSC canbe depicted, as shown in Fig. 5(b)–(d), and are named boost-type, buck–boost-type, and SEPIC-type PCSCs, respectively.

IV. PRINCIPLE OF SYNTHESIZING MICS

The MICs can be formed by inserting the PVSCs or thePCSCs into the PWM converters. For convenience of illustra-tion, the PWM converter is referred to as the prime PWM con-verter. After the PVSC or PCSC is inserted into the prime PWMconverter, the inserted PVSC or PCSC along with a portion ofthe prime PWM converter will form another PWM converter,which is called the pulsating-source-derived (PS-derived) con-verter. In the prime PWM converters, the energy buffer portionand the output portion are the two feasible locations for a PVSCor a PCSC to be inserted into. For different types of the PS cells

(the PVSCs or the PCSCs), the rules for synthesizing the MICsare distinct.

A. Rules for Synthesizing MICs With PVSCs

As mentioned previously, a PVSC that is composed of apulsating voltage source and a parallel diode can be insertedinto a prime PWM converter to yield an MIC. If the PVSCis connected in parallel with one of the branches of the primePWM converter, the voltage across the connected branch willbe clamped by the pulsating voltage source. Thus, the PVSCand the branch of the prime PWM converter must be connectedin series to avoid this situation. A branch in either the energybuffer portion or the output portion of the prime PWM convertercan be a candidate for a PVSC to be connected in series with it.

When a PVSC is introduced into the energy buffer portion of aprime PWM converter, it cannot be connected in series with anyother voltage buffer since the diode in the PVSC will block thebidirectional current flow of the connected voltage buffer in onedirection. Thus, a PVSC can be connected in series with a currentbuffer only when it is introduced into the energy buffer portionof a prime PWM converter to form an MIC, as conceptuallyillustrated in Fig. 6(a). In addition, it should be noted that theorientation of a PVSC must have the unidirectional current flowof the connected current buffer flowing out of the positive end ofthe PVSC, so that the diode in the PVSC would not prohibit theunidirectional current of the current buffer from flowing, i.e., thecurrent buffer shown in Fig. 6(a) will never be open-circuited.

In the case of inserting a PVSC into the output portion of aprime PWM converter, the PVSC must be connected in serieswith the current sink rather than the voltage sink, as depicted inFig. 6(b). Similarly, to circulate the current flow of the currentsink, the PVSC and the current sink are connected in series withthe current of the current sink flowing out of the positive end ofthe PVSC.

Furthermore, each of the input-to-output port pair of an MICcan be regarded as an individual PWM converter separately andall of the input sources can deliver power to the load either in-dividually or simultaneously through the MIC, i.e., the primePWM converter and the PS-derived converter can operate indi-vidually or simultaneously. To meet this requirement, a PVSCmust be connected within a mesh containing an output sink of aprime PWM converter when it is introduced into a prime PWMconverter.

According to the previous discussion, the rules for synthesiz-ing MICs with PVSCs can be summarized as follows.Rule 1: When a PVSC is introduced into the energy buffer

portion of a prime PWM converter, it must be connectedin series with a current buffer and have the current ofthe connected current buffer flowing out of its positiveend.

Rule 2: When a PVSC is inserted into the output portion of aprime PWM converter, it must be connected in serieswith a current sink and have the current flow of theconnected current sink flowing out of its positive end.

Rule 3: A PVSC must be connected within a mesh containingan output sink.



Fig. 10. MICs synthesized by the Cuk-type PVSC with different prime converters. (a) Buck converter. (b) Buck–boost converter. (c) Cuk converter. (d) Zetaconverter. (e) SEPIC converter.

B. Rules for Synthesizing MICs With PCSCs

Unlike the series connection between a PVSC and a branchof a prime PWM converter, a PCSC and a branch of a primePWM converter must be connected in parallel to form an MIC.This is because the pulsating current source of the PCSC willclamp the current through the connected branch of the primePWM converter when the PCSC is connected in series with oneof the branches of the PWM converter.

First of all, if a PCSC is connected in parallel with a currentbuffer of the energy buffer portion of a prime PWM converterto develop an MIC, the diode in the PCSC will short-circuit thebidirectional voltage blocking of the connected current buffer inone direction. Hence, a PCSC should be connected in parallelwith a voltage buffer when it is inserted into the energy bufferportion of a prime PWM converter to yield an MIC, as depictedin Fig. 7(a). The feasible orientation of a PCSC can be foundto possess the outgoing current terminal of the PCSC tied tothe positive end of the voltage buffer. Consequently, the diodein the PCSC can always block the voltage discrepancy betweenthe pulsating current source and the connected voltage buffer,

and furthermore, the connected voltage buffer will never beshort-circuited.

Fig. 7(b) conceptually shows the feasible circuit configurationof a PCSC connecting to the output portion of a prime PWMconverter. In the figure, the PCSC is connected in parallel withthe voltage sink rather than the current sink. Similarly, it shouldbe noted that the PCSC needs to be connected across the voltagesink with the outgoing current terminal of the PCSC tied to thepositive end of the voltage sink.

According to the definition of an MIC described in Section I,both the input sources of the prime PWM converter and thePS-derived converter should be able to deliver power to the loadeither individually or simultaneously. To fulfill this capability, aPCSC must form a mesh with an output sink of a prime PWMconverter when it is inserted into a prime PWM converter.

Based on the previous discussion, the rules for synthesizingMICs with PCSCs can be summarized as follows.Rule 1: When a PCSC is introduced into the energy buffer

portion of a prime PWM converter, it must be con-nected in parallel with a voltage buffer and its outgoing



Fig. 11. MICs synthesized by the zeta-type PVSC with different prime converters. (a) Buck converter. (b) Buck–boost converter. (c) Cuk converter. (d) Zetaconverter. (e) SEPIC converter.

current terminal must tie to the positive end of the volt-age buffer.

Rule 2: When a PCSC is inserted into the output portion of aprime PWM converter, it must be connected across avoltage sink with its outgoing current terminal tied tothe positive end of the voltage sink.

Rule 3: A PCSC must form a mesh with an output sink.

V. SYNTHESIS OF MICS

An MIC can be developed by introducing a PVSC or a PCSCinto a prime PWM converter. For different types of PS cells(the PVSCs and the PCSCs), the synthesis procedures of theMICs are distinct from each other. In this section, the synthesisprocedures for developing the MICs with PVSCs and PCSCswill be presented separately according to the rules addressed inthe prior section, from which two families of the MICs classifiedby the PVSCs and the PCSCs will be developed.

A. Generation of MICs With PVSCs

Based on the rules listed in Section IV-A, the synthesis pro-cess of the MICs with PVSCs is summarized as follows.

Step 1: Choose one of the PVSCs shown in Fig. 4.Step 2: Select one of the six basic PWM converters as the prime

PWM converter that contains the current buffers or thecurrent sink.

Step 3: Insert the chosen PVSC into the selected primePWM converter according to rules 1 and 2 listed inSection IV-A.

Step 4: Verify whether the inserted PVSC obeys rule 3 listed inSection IV-A. The final version of an MIC can then beobtained.

An example for the synthesis of the MIC is illustrated inFig. 8, where the buck-type PVSC and the zeta converter areselected as a PVSC and a prime PWM converter, respectively.In Fig. 8(a), the zeta converter possesses a current buffer and acurrent sink so that it has two feasible positions for the buck-type PVSC to be inserted into. When the buck-type PVSC isinserted into the output portion of the zeta converter, as shownin Fig. 8(b), it must be connected in series with the current sinkof the zeta converter according to rule 2 listed in Section IV-A.In this figure, the buck-type PVSC is connected within a meshcontaining the current sink of the zeta converter so that thePS-derived converter can operate individually. The MIC that



Fig. 12. Illustration of the MIC derived from the boost-type PCSC and the SEPIC converter. (a) Boost-type PCSC and the SEPIC prime converter. (b) PCSC isinserted into the output sink of the prime converter. (c) Synthesized MIC with appropriate circuit configuration. (d) PCSC is inserted into the voltage buffer of theprime converter. (e) Synthesized MIC with appropriate circuit configuration.

Fig. 13. MICs synthesized by the boost-type PCSC with different prime converters. (a) Boost converter. (b) Buck–boost converter. (c) SEPIC converter.



Fig. 14. MICs synthesized by the buck–boost-type PCSC with different prime converters. (a) Boost converter. (b) Buck–boost converter. (c) SEPIC converter.

Fig. 15. MICs synthesized by the SEPIC-type PCSC with different prime converters. (a) Boost converter. (b) Buck–boost converter. (c) SEPIC converter.

is derived from combining the buck-type PVSC and the zetaconverter can be obtained and depicted in Fig. 8(c). On theother hand, Fig. 8(d) shows the case of introducing the buck-type PVSC into the energy buffer portion of the zeta converterin which the buck-type PVSC is connected in series with thecurrent buffer of the zeta converter. The final version of theconverter is depicted in Fig. 8(e).

Investigation of Fig. 8(d) reveals that the buck-type PVSC isnot connected within a mesh containing the output sink of thezeta converter so that the PS-derived converter cannot operateindividually, i.e., the buck-type PVSC can deliver power to the

load only when the zeta converter operates. This kind of MIC isdefined as a quasi-MIC because it lacks the property of transfer-ring power individually. The further investigation of quasi-MICwill be addressed later.

By following the same synthesis procedure, the rest of theMICs with buck-type, Cuk-type, and zeta-type PVSCs can bealso generated, and are shown in Figs. 9–11, respectively. InFig. 9(b), the MIC circuitry had been published by the au-thor and used for the renewable energy applications. Detailsof the operation principle and control strategy can be found in[26].



Fig. 16. Quasi-MIC derived from the buck-type PVSC and the zeta converter.

Fig. 17. Quasi-MIC derived from the Cuk-type PVSC and the zeta converter.

Fig. 18. Quasi-MIC derived from the zeta-type PVSC and the zeta converter.

B. Generation of MICs With PCSCs

Similarly, the synthesis procedure of the MICs with PCSCscan be summarized by the following steps.Step 1: Choose one of the PCSCs shown in Fig. 5.Step 2: Select one of the six basic PWM converters as the prime

PWM converter that contains the voltage buffers or thevoltage sink.

Step 3: Insert the chosen PCSC into the selected prime PWMconverter according to rules 1 and 2 listed in Section IV-B.

Step 4: Verify whether the inserted PCSC obeys rule 3 listed inSection IV-B. The final version of an MIC can then beobtained.

An example is demonstrated to describe the synthesis pro-cedure of the MICs with PCSCs. Derivation of this MIC isillustrated in Fig. 12, where the SEPIC converter is selected asthe prime PWM converter for the boost-type PCSC to be in-serted into. For convenience of derivation, the boost-type PCSCis lumped into an element and the SEPIC converter is redrawnto a topological structure form, as shown in Fig. 12(a). In thisfigure, it can be seen that the SEPIC converter has two feasiblepositions, the voltage buffer and the voltage sink, for the boost-

type PCSC to be introduced into. According to rule 2 listedin Section IV-B, the boost-type PCSC is connected in parallelwith the voltage sink of the SEPIC converter, as depicted inFig. 12(b). In addition, since the boost-type PCSC forms a meshwith the voltage sink of the SEPIC converter, the PS-derivedconverter can deliver power to the load individually. By replac-ing the block diagram of the boost-type PCSC with its actualcircuit, the MIC shown in Fig. 12(c) can be obtained. Althoughthe schematic diagram shown in Fig. 12(c) seems to be trivialand can be generated just by connecting the outputs of the boostand the SEPIC converters in parallel, it is indeed an MIC that isdeveloped by following the synthesis procedure described previ-ously in this section, i.e., the proposed approach for developingthe MICs can explore more physical insights into the convertershown in Fig. 12(c).

On the other hand, Fig. 12(d) shows that a PCSC is connectedin parallel with the voltage buffer of the SEPIC converter when itis inserted into the energy buffer portion of the SEPIC converter.In Fig. 12(d), it can be seen that the boost-type PCSC does notform a mesh with the output sink of the SEPIC converter. Thiswill lead to the result that the boost-type PCSC converter cannotbe operated individually, which makes the derived converterbecome a quasi-MIC. By replacing the block diagram of theboost-type PCSC with its actual circuit, the final version of thequasi-MIC is obtained, and is depicted in Fig. 12(e).

By following the same synthesis procedure, the rest of theMICs with boost-type, buck–boost-type, and SEPIC-type PC-SCs can be also generated, and are shown in Figs. 13–15, respec-tively. It is worth mentioning that the circuit topology shown inFig. 13(a) is the multiple-input dc–dc power converter for hybridvehicles proposed in [18]–[22].

C. Quasi-MICs

As described previously, the MICs possess the feature thatall of their input sources can deliver power to the load eitherindividually or simultaneously. When the PVSCs or the PCSCsare introduced into the output portions of the prime PWM con-verters, the derived converters will have this feature and becomeMICs. However, when the PVSCs or the PCSCs are inserted intothe energy buffer portions of the prime PWM converters, not allof the derived converters can be identified as the MICs. Forinstance, when the buck-type PVSC is connected in series withthe current buffer of the zeta converter, as shown in Fig. 8(d), itis not connected within a mesh containing the output sink of thezeta converter. This will lead to the result that the input sourceof the buck-type PVSC cannot deliver power directly to theload but only to the energy buffer. In other words, it can deliverpower only to the load when the input source of the prime PWMconverter delivers power to the load simultaneously. Therefore,the derived converter shown in Fig. 8(e) will be classified as aquasi-MIC. The quasi-MICs synthesized with different types ofthe PVSCs and the PCSCs are shown in Figs. 16–21.

VI. DISCUSSION

For clarity, the MICs and the quasi-MICs generated in thispaper are tabulated in Table I. In the table, the figure number



Fig. 19. Quasi-MICs synthesized by the boost-type PCSC with different prime converters. (a) Cuk converter. (b) Zeta converter. (c) SEPIC converter.

Fig. 20. Quasi-MICs synthesized by the buck–boost-type PCSC with different prime converters. (a) Cuk converter. (b) Zeta converter. (c) SEPIC converter.

denotes the schematic diagram of the MIC or the quasi-MICdeveloped from the corresponding PS cell along with the primePWM converter. The nonunderlined figure numbers denote thederived converters that are MICs, while the underlined ones des-ignate the converters that are quasi-MICs. For the PVSCs, theymust be connected in series only with the current buffers or thecurrent sinks so that no MICs or quasi-MICs can be generatedwhen they are introduced into the boost converter. Similarly,no MICs or quasi-MICs can be developed when the PCSCs areinserted into the buck converter, since the buck converter doesnot possess any voltage buffer or voltage sink.

In Table I, some schematic diagrams of MICs are found tobe duplicated. In the case of inserting one of the PVSCs into aprime PWM converter, the duplicated circuit diagrams might berecognized when the prime PWM converter is the one amongthe buck, Cuk, and zeta converters.

In general, a PVSC-derived MIC can be considered as thecombination of the prime PWM converter and the PS-derivedconverter that are any two of the three converters (buck, Cuk, andzeta converters). Three duplicated MICs can be found when thecircuit diagrams of the prime PWM converter and the PS-derivedconverter are exchanged. By applying the same principle to the



Fig. 21. Quasi-MICs synthesized by the SEPIC-type PCSC with different prime converters. (a) Cuk converter. (b) Zeta converter. (c) SEPIC converter.

TABLE IFIGURE NUMBERS FOR MICS INCLUDING QUASI-MICS AND DUPLICATED MICS

PCSC-derived MICs, three more duplicated MICs can also beobtained. In Table I, the duplicated MICs are marked by thesame symbol. For example, Figs. 13(b) and 14(a) are identical.

As compared to the circuits formed by two PWM converterswith their outputs paralleled, the MICs developed in this papercan save the amount of inductors and/or capacitors. For instance,the circuit formed by two buck converters with their outputs tiedtogether possesses two inductors at the output side while thebuck–buck MIC shown in Fig. 9(a) has only one inductor at theoutput portion.

VII. CONCLUSION

In this paper, the pulsating voltage source along with theparallel-connected diode and the pulsating current source alongwith the series-connected diode were defined as the PVSC andPCSC, respectively. From these circuit configurations, two fam-ilies of PS cells can be derived. According to the circuit charac-teristics of the PVSCs and PCSCs, rules for synthesizing MICs

with PVSCs and PCSCs were presented. In addition, to ensurethat all of the input sources deliver power to the load either indi-vidually or simultaneously, a PVSC must be connected within amesh containing the output sink and a PCSC must form a meshwith the output sink of a prime PWM converter. By using thepresented rules, two families of MICs have been generated.

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Yuan-Chuan Liu was born in Chia-Yi, Taiwan, in1973. He received the B.S. and Ph.D. degrees fromNational Chung Cheng University, Chia-Yi, Taiwan,in 1996 and 2006, respectively, both in electricalengineering.

From 2006 to 2007, he was a Senior Engineer withNuLight Technology Company, Tainan, Taiwan. In2008, he joined Acbel Polytech, Inc., Taipei, Taiwan,as a Senior Engineer. His current research interests in-clude developing and designing of converter topolo-gies, power-factor correctors, and electronic ballasts.

Yaow-Ming Chen (S’95–M’97–SM’06) received theB.S. degree from National Cheng-Kung University,Tainan, Taiwan, in 1989, and the M.S. and Ph.D. de-grees from the University of Missouri, Columbia, in1993 and 1997, respectively, all in electrical engi-neering.

From 1997 to 2000, he was an Assistant Professorwith I-Shou University, Kaohsiung, Taiwan. From2000 to 2008, he was with National Chung ChengUniversity, Chia-Yi, Taiwan. In 2008, he joined Na-tional Taiwan University, Taipei, Taiwan, where he is

currently an Associate Professor in the Department of Electrical Engineering.His current research interests include power electronic converters, renewableenergy, power system harmonics and compensation, and intelligent control.


A Systematic Approach to Synthesizing Multi-Input DC–DC Converters.pdf

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