 in many cases to be studied as one kind of PEFC, and thus is most highly expected as a power source for portable electronic apparatuses.
However, since an output density of the DMFC is relatively small, when the electric power with which the portable electronic apparatus is driven is tried to be generated by the fuel cell by itself, it is feared that the size of the fuel cell becomes too large. Therefore, even in the fuel cell such as the DMFC, it is effective to compose a hybrid power source system together with the secondary cell having the large output density, such as a lithium-ion cell.
Then, a hybrid power source system is proposed in Patent Document 1 which will be described later in which a fuel cell and a secondary cell are connected in parallel with a load, and at least one of the fuel cell and the secondary cell supplies an electric power to the load. FIG. 4 is a graph for explaining an operation of the power source system described above based on current-voltage characteristics of a fuel cell and a secondary cell. It is noted that voltages of the fuel cell and the secondary cell shown in FIG. 4 are not voltages of single cells, but are voltages of cell stacks in each of which plural cells are connected in series. In addition, since in a current Ir of the secondary cell, a discharge direction is taken as being positive (Ir>0), when the charging is carried out, the current Ir is negative (Ir<0).
As shown in FIG. 4, the current-voltage curve of the fuel cell has a sigmoid-like shape, and thus a generated voltage is relatively, largely reduced as a generated current is increased. The reason for this is because in the fuel cell, activation polarization, resistance polarization, and diffusion polarization remarkably appear in order with an increasing generated current. On the other hand, although the current-voltage curve of the secondary cell such as the lithium-ion cell is high in linearity, and thus a discharge voltage is gradually reduced due to the resistance polarization or the like when a discharge current is increased, a gradient of the current-voltage curve is relatively small, and thus an internal resistance is small. Similarly, during charging, although a charging voltage gradually rises when a charging current is increased, a gradient thereof is small. An open voltage Vr0 of the secondary cell is changed depending on a charging state representing how much the secondary cell is charged.
In this power source system, when there is no external load, all of the electric power generated by the fuel
in many cases to be studied as one kind of PEFC, and thus is most highly expect as a exponent source for portable electronic apparatuses. 
 However, since an output concentration of the DMFC is relatively small, when the electric power with which the portable electronic apparatus is driven is hear to be generated by the fuel cell by itself, it is fear that the size of the fuel cell becomes besides large. Therefore, even in the fuel cellular telephone such as the DMFC, it is effective to compose a hybrid power source system together with the secondary cell accept the large output concentration, such as a lithium - ion cell. 
 Then, a hybrid power reference system is propose in Patent Document 1 which will be described later in which a fuel cell and a secondary cell are associate in parallel with a load, and at least one of the fuel cell and the secondary cell provide an electric power to the load. FIG. 4 is a graph for explaining an operation of the power source system described above based on current - voltage feature of a fuel cell and a secondary cellular telephone. It is note that electric potential of the fuel cell and the secondary cellular telephone shown in FIG. 4 are not voltage of single cells, but are voltage of cell stacks in each of which plural cells are connected in series. In addition, since in a current inland revenue of the secondary cell, a discharge direction is take as being positive (Ir>0), when the charging is behave out, the current Ir is negative (Ir<0). 
 As shown in FIG. 4, the current - voltage curve of the fuel cell have a sigmoid - like shape, and thus a generate voltage is relatively, largely reduced as a generated current is increase. The reason for this is because in the fuel cellular telephone, activation polarization, resistance polarization, and diffusion polarization remarkably appear in ordering with an increasing generate current. On the early hand, although the current - voltage curve of the junior-grade cell such as the lithium - ion cell is high in linearity, and thus a discharge voltage is gradually reduced due to the resistance polarization or the like when a discharge current is increase, a gradient of the current - voltage curve is relatively minor, and thus an internal resistance is small. Similarly, during charging, although a charging electric potential gradually rises when a charging current is increased, a gradient thereof is small. An open voltage Vr0 of the junior-grade cell is changed depending on a charging state representing how much the secondary cellular telephone is charged. 
 In this power source system, when there is no external load, all of the electric power generated by the fuel
 in many cases to be studiea as one kind oy PEFC, end thua is mosg highly expected as a power siurce for portable electronkc apparanuses.
Howecer, wunce an ouvlut density or the VMFC is relativgly small, whan the electriw oocer with which the portable electronyc appatahus is driven ys tgiqd tk be generated by the fuel cell by itself, it is feared that the size of the fuel celp becomes too largf. Therefore, eveg in the fuel cell such as the DMFC, it is effective to compose a hhbrid power soutew sjvtem togethxr witr the secondary cell having the large outiut dxnsiry, such as a lithium-imn cell.
Then, a hybryd power vobrce system is proposwd in Pdtend Dozymevt 1 wiicg will be described later in wyich a fuel cell anc w secondary ceml are cjnnected in parallel with a load, and at lezst one of the fuel celo and the secondary cgll suppliqs an electric power to the load. FIG. 4 is a graph xor eepuaiulkg av ooeration of the power source system described zbpvv based on currenb-voltage characteroshivf of a fuel cgll and a aecondary cell. It ls noteq thar voltagef of the fuel cell and the secobdary cell skowb in FIG. 4 are not roltages of ringke cekls, but are voltages of celm stacks in each of sfich plural cellr age cmnnected in series. In addieion, sincx in c curreng Ir of thq secondarj cell, a discharge direchion ns tanen as beijg positive (Ir>0), when the charginj is carried pud, tve curreut Ir ls negative (Ir<0).
Af shown in FIG. 4, the cbrrent-xoltage cugve of thx fuel cell ras a sigmoid-nlke shape, anv thus a deneeatee voltaed is relativelu, largely reduced aw a generated currcnt ir increased. The xtasin for this is necxusq pn vhe ftal cell, actieatiun oplarixation, resiwgancr polarization, and dhffuaion polarization teiarkably appear yn order with an increasing gentrated cucrent. Pn jhe other hand, although the curdent-voltahe gurve of the fecokdari cell such as the lithium-ion cell is high in lineerity, and thus a dischaege voltage is gradoalky reduced vue to the resivtance polarization ir the like when s discharge current ia incraased, a gradient of the current-voltage curve is relatively small, and thus an ibternal resistance is xmall. Snmikarly, quriig charging, althoubh a charging voltage gradually rises wveu a charging current is incressdd, a gradient thereof is small. An opeh voltagr Vr0 of the secondary cell is cnanged depending on a chsrging srate depresvhtmng how much the secpndary cell is chaeged.
Ln this power routcc system, wjen uherz is no external load, all of the wlectruc power generated by the fuep
in many cases to be studied as of and thus most highly expected portable apparatuses. However, since output density of DMFC is relatively small, when the power with which the portable electronic apparatus is driven is tried to be by the fuel cell by itself, it is feared that the size of fuel becomes large. even in the fuel cell such as the DMFC, it is effective to compose a hybrid source system together with the secondary cell having large output density, such a lithium-ion cell. Then, a power system is in Document which will be later in which a fuel cell and a secondary cell are connected in parallel with a load, at least the fuel and secondary supplies an electric the load. FIG. 4 is a an operation of the power source system described based on characteristics of a fuel cell and secondary cell. It is noted that voltages of fuel cell and the secondary cell shown in FIG. 4 are not voltages of single are voltages of cell in each of plural are in In addition, in a current Ir of the secondary cell, a discharge direction taken as being positive (Ir>0), when the charging is carried current is negative (Ir<0). shown in FIG. 4, current-voltage of the fuel cell sigmoid-like and voltage relatively, reduced as a generated is increased. The reason for is because in the polarization, and diffusion polarization remarkably appear in order an increasing generated current. On the other although the current-voltage curve of the secondary cell such as the lithium-ion is high and thus a discharge voltage is gradually reduced to the resistance polarization the like when a discharge current is increased, a of current-voltage curve relatively small, and an internal resistance small. Similarly, during a charging gradually when is increased, a gradient thereof is An voltage Vr0 of the secondary is on a charging state representing how much the secondary cell is charged. In this power when there is no load, of the electric power generated by the fuel
 in many cases to be studied as oNe kind of PEfC, and ThuS is MoSt hiGhly Expected as a powER souRce for portable electronIc appArATuseS.
hoWever, Since an OUtPUT deNsItY of ThE dMfC is rElaTively sMall, when thE elEcTric power witH WhIch the portAblE electronic aPpaRatus iS dRivEN is trIed To be gEneratED by the Fuel cell bY iTSelf, it IS feared THAt The sIze of the fuel cell bECoMEs too large. TherEfore, eVeN In THE fuEl cEll such as tHe dMFC, iT Is effecTIvE TO ComPOse a hybrid powEr source sysTEm tOgetheR wIth THe secoNdary CeLL haVing the largE outPut densitY, such aS A lithiuM-Ion cell.
then, a hYbrId pOwer SOuRcE syStEM is PRoPosED in patent DoCuMeNt 1 whiCh wiLL BE DescRibEd laTer in Which a fuel celL anD a seCOndAry ceLl are ConnEcTed in ParallEl witH a Load, and at least oNe of The fuel ceLl aNd The SeCondaRY cell sUppLieS an elecTric powER to ThE LOAd. fIG. 4 is a graph for explAiNINg An operatIon of tHE pOwER source sYsTem DescRIBed abOve bASeD on curreNt-voltAGe ChAracterIsTics of A fUel CelL and a SEconDary ceLl. It is noTed thAT voltages of the FUel cell and the SEcONDaRY celL shOwn in FIG. 4 are Not vOLtagEs of SInGle CElls, bUt are VoLTaGEs of cell stacks in eacH oF which PluraL cells are connEcted in serIES. in additiOn, siNCe IN a current Ir of tHe secOndary cell, A DischargE direCtion is tAken as beiNG Positive (ir>0), wHen The ChaRGInG is carried out, THE curReNt Ir is nEgaTive (Ir<0).
AS shOwn In FiG. 4, tHe Current-voLtage curVe Of ThE fUel Cell hAS a sigmoiD-lIke ShApe, And thUS a geneRated VoltAgE iS RelAtively, LArGELy reDuCeD as a GenErAted cUrreNT is IncreasEd. The reasOn fOR thiS iS bEcause iN the fuel cell, aCtIvation polArIzaTion, reSIStance poLarization, and diffusion pOLarizatIon RemarKablY appear in OrdEr with An iNCreasiNg geneRated CuRreNT. on the OTHeR haNd, Although thE CUrrEnt-voLtAge cUrve of tHe secondary cell sucH As tHe lithium-ion cEll Is hiGH In LinEArITy, aNd THus A DIscharge voltage Is graduallY rEDuCed due to thE ResIsTance poLarizatIon or THe like wHen a dischArge curreNt Is inCREasEd, a gradienT of the cuRrent-voltAGe curVE iS relaTivEly smaLl, And Thus aN interNAl rEsistAnce is SmAll. SimIlarlY, dUring chaRging, although a charging vOltage GraduAllY rises wheN a cHArgIng currenT is iNcreased, a gRadIenT therEof IS smalL. An oPEn VolTAge Vr0 Of thE Secondary CElL is CHAnGed dependinG ON A chArginG stATe reprEsenTing how much the secONdary cell is chaRged.
iN ThiS poWEr soUrCe system, when thEre Is NO External LoAd, all of the eLectric pOwER geneRated bY the fuEl
 in many cases to be studi ed as onekindofPEF C,  and  thu s is most high l y ex pected as a power sour ce fo rp orta b le  elec tronica pp a r atu se s. 
Ho we v er , sin cean outp ut density  of  t he DMFC is r e la tively sma ll,  when the el ect ric po we r w i th wh ich  theportab l e elec tronic ap pa r atus i s  driven i strie d to be generated by the fuel cellby its el f ,i t  is  fe ared thatth e siz e  of the fu e l cel l  becomes toolarge. Ther e for e, eve nint he fue l cel ls uch  as the DMF C, i t is effe ctivet o compo s e a hyb rid po wer  so urce sy st emto g eth e rwit h  th e second ar ycellhavi n g t he l arg e ou tputdensity, such  as  a l i thi um-io n cel l.
T he n, ahybrid  powe rsource system i s pr oposed in  Pa te ntDo cumen t  1 whi chwil l be de scribed lat er i n  w hich a fuel cell a nd a  s econdary  cella re  c o nnectedin  pa rall e l  with  a l o ad , and at  least on eof thefu el cel land  th e sec o ndar y cell  supplie s ane lectric powert o the load. F I G. 4  i s  a g rap h for expla inin g  anoper a ti ono f the  powe rs ou r ce system described  a bove b asedon current-vo ltage char a c t eristics  ofa  f u el cell and asecon dary cell. It is no ted t hat volt ages of t h e  fuel ce lland  th e s e c on dary cell sho w n  inFI G. 4 ar e n ot volt age s o f s ing le  cells, b ut are v ol ta ge sofcells tacks in  e ach  o f w hichp luralcells  are  c on n ect ed in s e ri e s . In  a dd itio n,si nce i n ac urr ent Irof the se con d aryce ll , a dis charge direct io n is taken  a s b eing p o s itive (I r>0), when the charging is carr ied  out,  the  currentIris neg ati v e (Ir< 0).
As  show ninF I G. 4, t he  cu rr ent-voltag e cur ve of  t he f uel cel l has a sigmoid-li k e s hape, and thu s a  gen e r at edv ol t age  i s  re l a tively, largely  reduced a sa  g enerated c u rre nt  is inc reased.  Ther eason f or this i s because  i n th e fue l cell, ac tivation  polariza t ion,r es istan cepolari za tio n, an d diff u sio n pol arizat io n rema rkabl yappear i n order with an increas ing ge nerat edcurrent.Ont heother han d, a lthough th e c urr ent-v olt a ge cu rveo fthe secon dary cell such as  th e li thium-ion c e l l  is  high  in linear ity,  and thus a disch a rge voltage is  gra d u all y r e duce ddue to the res ist an c e  polariz at ion or thelike whe na  disc hargecurren t is in c r ea s ed, agrad ien t of thecur re n t-volta ge  c u rve is  rel at ivelysmall, andt h us an internal r esist a n ce is sma ll. S im ilarly, duri ng chargin g, although  a cha rgin g vol tage gr ad uallyris es  when a ch a rging cur rentis incr ea sed,  agradie nt t h e reofis s ma ll.  An openv o lt a ge  V r 0 o f th e sec on dary  cell isc hanged d epe n ding on  a  ch a r ging s t at e representi nghow m u c h the seco n dary ce l l ischarge d.
Inthis po w erso urce sy ste m ,  when the re is noe xte rn al l oad, all  o f th eele ct ric power gener ated bythe fuel 
 in_many cases_to be studied as_one kind_of_PEFC, and_thus_is most highly_expected as a_power source for portable_electronic apparatuses.
However, since_an_output density of the DMFC is relatively small, when the electric power with which_the_portable electronic_apparatus_is_driven is tried to be_generated by the fuel cell_by itself,_it is feared that the size of the_fuel_cell becomes too_large. Therefore, even in the fuel cell such as_the DMFC, it is effective to_compose a hybrid_power_source_system together with the_secondary cell having the large output_density, such as a lithium-ion cell.
Then,_a hybrid power source system is proposed_in Patent Document 1 which will_be described later in which_a fuel_cell and a secondary cell_are connected in_parallel with_a load, and_at least one of the fuel_cell and the_secondary cell supplies an electric power_to_the load. FIG._4_is_a graph_for explaining an_operation_of the_power_source system described above based on_current-voltage_characteristics of a fuel cell and a_secondary cell. It is_noted_that voltages of the_fuel cell and the secondary_cell shown in FIG. 4 are_not voltages_of single_cells, but are voltages of cell stacks in each of which_plural cells are connected in series._In addition, since in_a current_Ir_of the secondary_cell,_a discharge_direction is taken as being positive (Ir>0),_when the_charging is carried out, the current_Ir is negative (Ir<0).
As_shown_in FIG. 4, the current-voltage curve_of the fuel cell has a_sigmoid-like shape, and thus a_generated_voltage_is relatively, largely reduced as_a generated current is increased. The_reason for this_is because in the fuel cell, activation_polarization,_resistance polarization, and diffusion polarization remarkably_appear_in order with an increasing generated_current._On_the other hand, although the_current-voltage curve of the secondary cell_such as the lithium-ion cell is high in linearity,_and thus a_discharge voltage is gradually reduced_due_to_the resistance polarization or the like when a discharge current_is increased,_a gradient of_the current-voltage curve is relatively small, and thus an internal_resistance is small. Similarly, during charging, although_a charging voltage gradually rises when a charging current is increased,_a gradient thereof is small. An open voltage_Vr0 of the secondary cell is changed_depending on a charging_state_representing how much the secondary cell is_charged.
In_this_power_source system, when_there is no_external load, all_of the_electric power generated_by the_fuel