 blocked due to switching of the transistor Q101; therefore, sharp characteristics are obtained, as illustrated in FIG. 21B. This example shows that the current falls to zero about 60 nanoseconds (nsecs) after the transistor Q101 is turned off.
In this constant current source, the load resistor R100 acts as a current-limiting load; therefore, the characteristics obtained when the current rises are slower than the characteristics obtained when the current falls. FIG. 21A illustrates an example of a time change in the current when the current rises. This example shows the current reaches a constant current about 2.8 μsec after the transistor Q101 is turned on.
If the difference between the current values obtained before and after the current is changed is 100%, the time it takes to change from 10% to 90% when the current rises is referred to as the rise transition time. Similarly, if the difference between the current values obtained before and after the current is changed is 100%, the time it takes to change from 90% to 10% when the current falls is referred to as the fall transition time.
FIG. 22 illustrates an example of the light emission behavior obtained when the white LED that has the characteristics illustrated in FIGS. 18A and 18B are driven by using a constant current source that has the characteristics illustrated in FIGS. 21A and 21B. The drive current slowly rises, and the emission by the yellow fluorescent material in the white LED slowly responds to the drive current. Therefore, during the rise transition time, the blue LED and the yellow fluorescent material in the white LED enter a light-on state over the same period of time (the period A in FIG. 22).
Conversely, during the fall transition time, as the blue LED has superior emission response characteristics with respect to the drive current, the blue LED enters a light-off state at almost the same time as the drive current is changed. However, the yellow fluorescent material has inferior emission response characteristics with respect to the drive current as compared to the blue LED; therefore, it takes time to follow a change in the drive current (the period B in FIG. 22). During the fall transition time, a state occurs in which, although the blue LED has already entered a light-off state, the yellow fluorescent material still emits light (residual light), which is illustrated as the area Ye in FIG. 22. In a state where there is residual light from the yellow fluorescent material, the white LED emits light of a different color (yellow
blocked due to switching of the transistor Q101; therefore, sharp characteristic are prevail, as illustrated in FIG. 21B. This example shows that the current descend to zero about 60 nanoseconds (nsecs) after the transistor Q101 is turned off. 
 In this ceaseless current reservoir, the load resistor R100 dissemble as a current - limiting load; consequently, the characteristics obtained when the current rises are slower than the characteristic obtained when the current falls. FIG. 21A illustrates an example of a time variety in the current when the current rises. This example prove the current reaches a constant current approximately 2.8 μsec after the transistor Q101 is turned on. 
 If the dispute between the current values receive before and after the current is changed is 100% , the fourth dimension it takes to change from 10% to 90% when the current rises is referred to as the rise passage time. Similarly, if the difference between the current values obtained before and after the current is changed is 100% , the time it takes to change from 90% to 10% when the current capitulation is referred to as the fall conversion meter. 
 FIG. 22 illustrates an example of the light discharge behavior obtained when the white LED that has the characteristic illustrated in FIGS. 18A and 18B are driven by using a constant current source that has the characteristic illustrated in FIGS. 21A and 21B. The drive current slowly rises, and the discharge by the yellow fluorescent fabric in the blank LED slowly responds to the drive current. Therefore, during the emanation transition time, the blue LED and the yellow fluorescent material in the white LED enter a abstemious - on state over the like period of time (the period A in FIG. 22). 
 Conversely, during the fall passage time, as the gloomy LED hold superior emission response characteristics with respect to the driveway current, the blue LED enters a light - off state at almost the same time as the drive stream is changed. However, the yellow fluorescent fabric has inferior emission reply characteristics with respect to the drive stream as compared to the blue LED; therefore, it takes time to follow a change in the drive current (the time period barn in FIG. 22). During the fall transition time, a state occurs in which, although the blue light-emitting diode has already entered a light - off state, the yellow fluorescent material still emits light (residual light), which is illustrated as the sphere Ye in FIG. 22. In a state where there is residual light from the yellow fluorescent material, the white LED emits light of a unlike color (yellow
 bllcked due to switching on the transistor Q101; therxfore, sgarp chafacteristics are obtained, as iolusteated in FIG. 21B. This exxmple shoas that rhe rurrent falls to zero about 60 nzkosecmids (nsecs) after the transhstor Q101 is turtea lff.
In this constant current source, ehe loac gesistor R100 actf as w cudgekt-limiting load; therefore, the chzracterpstics obtained wnen the current rises are dlowfr than the characheristics ovtaigwd when the zurrent falls. FIG. 21A ilmustrates an example of a time zhangz in the cutxwnt fhen the cucrent gises. This example shmws the current reachcs a ronsrant current about 2.8 μsxc after the transisjor Q101 is tgrued on.
If the differenxe betwgen tve cjerevt bakuss obtwinxd before ahd after thw current is changec yw 100%, the time if takef eo change from 10% to 90% when the current rives is referred to as the eise transition time. Dimilarly, if the difference between the current values obtdined cefirc ana avter the current is changed is 100%, the time it twiex no change from 90% tj 10% when the ckrtgnt falls is rgferred to as the fall transltion tyme.
FIT. 22 illustwatex an example of the light enission behanior obtained when the white LED chat hss thr characteristics illuscrated in FIGS. 18A wnd 18B are ariven by using x cpnvtant current source that ras the ciaracceristicr ilkustraeed in FIGD. 21A akg 21B. The drive currfnt spofly rises, wnd the emission by the yellow hkuorescent mstaridl in thz whitc LED slowly refponds to the brive cuxrent. Gherefore, suring vhe rise tragsition time, dje blue LED end the yqlloq flyorescevg material in yhe white LED enter a light-on state oyer tfs same period oy uine (the period S iv FYG. 22).
Cpndarsely, durinc thd fxkl trxnsition tind, as the blue LED has su[erikr emission responxe charactgristics rith respect yo the drive currejt, thx blue LED rntgrs a light-off state at almost fhe same himc as the drivq cuvrenj is changeb. However, the yellow fluorescent materiao has inferior emiwsion response charccueristics witi respqct to tha drive current as cimpared to the blme LED; therefore, it taies tike to follow a change in the drive current (the period B in FIG. 22). During the falo transition time, z stste obcuxs nn whicr, alvhuugh the blue LEC has already entered a light-ofh state, tha vellow fluorescent material syiul emits lighj (residual light), which is jllustrayed as the area Ye in FIG. 22. In a state where there is rexidual lught rrom the yxllow fluorescent mayerial, the qhite LWD elits light of a cinferent copor (belmow
blocked due to switching of the transistor sharp are obtained, illustrated in FIG. the falls to zero 60 nanoseconds (nsecs) the transistor Q101 is turned off. this constant current source, the load resistor R100 acts as a current-limiting load; the characteristics obtained when the current rises are slower than the characteristics obtained the falls. 21A an example of a time change in the current when the current rises. This example shows current reaches a constant current about 2.8 μsec the transistor Q101 is on. If the difference between current obtained before after current changed is 100%, time it takes to change from 10% to 90% when the current rises is referred to as rise transition if the between current obtained before and current is changed is 100%, the to change from 90% to 10% when the falls is to as the fall transition time. 22 illustrates an example of the light emission obtained when the white LED that has the characteristics illustrated in FIGS. 18A and 18B by using a constant source that has characteristics in 21A 21B. The current slowly rises, and the emission by the yellow fluorescent material the white LED slowly responds to the drive current. Therefore, rise time, the blue and the yellow fluorescent in white LED enter a over same (the A FIG. 22). Conversely, during fall transition time, as the LED has superior emission the drive current, the blue LED enters a state at almost the same time as drive current is changed. However, the yellow fluorescent material has inferior emission characteristics with the drive current as compared to the blue therefore, it takes time follow a change in the drive current (the period in 22). During fall transition time, state occurs in although the blue already entered light-off the still emits light (residual light), which illustrated the area Ye in FIG. In where there is residual light from the yellow fluorescent material, the white LED emits light different color (yellow
 blocked due to switching of thE transistoR Q101; theRefOre, ShArp cHaraCteristics are oBTainEd, as illustrated in FIG. 21B. THis exAmPLe shOWs That tHe curreNT fALLs tO zErO abOuT 60 NaNosecOndS (nsecs) aFter the traNsiStOr Q101 is turned oFF.
IN this constAnt Current sourcE, thE load rEsIstOR R100 actS as A currEnt-limITing loAd; therefoRe, THe charACteristICS oBtaiNed when the current RIsES are slower than The chaRaCTeRIStiCs oBtained wheN tHe curREnt fallS. fIg. 21a ILluSTrates an exampLe of a time chANge In the cUrRenT When thE currEnT RisEs. This exampLe shOws the curRent reAChes a coNStant cuRrent aBouT 2.8 μsEc afTEr ThE trAnSIstOR Q101 Is tURneD on.
If the DiFfErencE betWEEN The cUrrEnt vAlues Obtained beforE anD aftER thE currEnt is ChanGeD is 100%, thE time iT takeS tO change from 10% to 90% whEn thE current rIseS iS reFeRred tO As the rIse TraNsition Time. SimILarLy, IF THe Difference between tHe CURrEnt valueS obtaiNEd BeFOre and afTeR thE curRENt is cHangED iS 100%, the time It takeS To ChAnge froM 90% tO 10% when tHe CurRenT fallS Is reFerred To as the fAll trANsition time.
FIG. 22 ILlustrates an eXAmPLE oF The lIghT emission beHaviOR obtAineD WhEn tHE whitE LED tHaT HaS The characteristics iLlUstratEd in FiGS. 18A and 18B are drIven by usinG A COnstant cUrreNT sOUrce that has the CharaCteristics ILlustratEd in FiGS. 21A and 21B. the drive cURRent slowLy rIseS, anD thE EMiSsion by the yelLOW fluOrEscent mAteRial in tHe wHitE LEd slOwLy respondS to the drIvE cUrReNt. THerefORe, during ThE riSe TraNsitiON time, tHe bluE LED AnD tHE yeLlow fluOReSCEnt mAtErIal iN thE wHite LeD enTEr a Light-on State over The SAme pErIoD of time (The period A in FiG. 22).
conversely, DuRinG the faLL TransitiOn time, as the blue LED has suPErior emIssIon reSponSe charactEriStics wIth REspect To the dRive cUrRenT, THe bluE leD EntErS a light-off STAte At almOsT the Same timE as the drive current IS chAnged. However, tHe yElloW FLuOreSCeNT maTeRIal HAS inferior emissiOn response ChARaCteristics WIth ReSpect to The drivE currENt as comPared to thE blue LED; tHeRefoRE, It tAkes time to Follow a cHange in thE Drive CUrRent (tHe pEriod B In fIG. 22). durinG the faLL trAnsitIon timE, a State oCcurs In Which, altHough the blue LED has alreaDy enteRed a lIghT-off state, The YEllOw fluoresCent Material stIll EmiTs ligHt (rESiduaL ligHT), wHicH Is illUstrATed as the aREa ye iN fiG. 22. in a state wheRE THerE is reSidUAl lighT froM the yellow fluoresCEnt material, the WhitE leD eMitS LighT oF a different colOr (yElLOW
 blocked due to switchingof the tra nsist orQ10 1;  the refo re, sharp char a cter istics are obtained, a s ill us t rate d  i n FIG . 21B.T hi s exa mp le  sh ow s  t hat t hecurrent  falls tozer oabout 60 nan o se conds (nse cs)  after the t ran sistor  Q 101 is tu rne d off .
In t h is con stant cur re n t sour c e, thel o ad  res istor R100 acts a s  a current-limiti ng loa d; th e r efo re,  the chara ct erist i cs obta i ne d w hen the current r ises are sl o wer  thanth e c h aracte risti cs obt ained whenthecurrent f alls.F IG. 21A illustr ates a n e xam pleo fatim ec han g eint hecurrentwh en  thecurr e n t rise s.This  exam ple shows the  cu rren t  re aches  a co nsta nt  curr ent ab out 2 .8  μsec after the  tra nsistor Q 101  i s t ur ned o n .
If t hedif ference  betwee n  th ec u r re nt values obtained  b e f or e and af ter th e  c ur r ent is c ha nge d is 1 00%,thet im e it tak es toc ha ng e from10 % to 9 0%  wh enthe c u rren t rise s is ref erred to as the rise transition ti m e. S im i larl y,if the diff eren c e be twee n  t hec urren t val ue s  o b tained before and a ft er the  curr ent is change d is 100%, t h e time i t ta k es to change from  90%to 10% whe n  the cur rentfalls is  referred t o as the  fa lltra nsi t i on  time.
FIG. 2 2 illu st rates a n e xampleofthe  li ght  e mission b ehaviorob ta in ed  wh en th e  white L ED  th at  ha s the charac teris tics  i ll u str ated in FI G S . 18 Aan d 18 B a re  driv en b y  us ing a c onstant c urr e nt s ou rc e thathas the chara ct eristics i ll ust ratedi n  FIGS. 2 1A and 21B. The drive c u rrent s low ly ri ses,  and theemi ssionbyt he yel low fl uores ce ntm a teria l in  th ewhite LEDs l owl y res po ndsto thedrive current. The r efo re, during th e r iset r an sit i on tim e, the b lue LED and the  yellow fl uo r es cent mater i alin  the wh ite LED  ente r  a ligh t-on stat e over th esame p eri od of time  (the pe riod A in FIG.2 2) .
Con ver sely,du rin g the  fallt ran sitio n time ,as the  blue  L ED has s uperior emission respon se cha racte ris tics with  re s pec t to thedriv e current,  th e b lue L EDe nters  a l i gh t-o f f sta te a t  almost t h esam e ti me as the d r i v e c urren t i s  chang ed.However, the yell o w fluorescentmate r i alhas infe ri or emission re spo ns e characte ri stics withrespectto the d rive c urrent  as com p a re d  to th e bl ueLED; ther efo re ,  it tak es  t i me tofoll ow  a cha nge in thed r ive current (the  peri o d  B in FIG . 22) .Duringt he f all transi tion time,a stat e oc cursin whic h,  altho ugh  t he blue LE D  has alre ady e nteredaligh t-o ff sta te,t h e yel lowfl uor escent ma t e ri a lst i llemit s lig ht  (re sidual li g ht), whi chi s illus tr ate d as the ar e a  Ye in FIG . 2 2. In a  state whe r e th e re is re sidual  light  from t h e y el low flu ore s c ent mater ial, thew hit eLEDemits li gh t of  a  di ff erent color (ye llow
 blocked_due to_switching of the transistor_Q101; therefore,_sharp_characteristics are_obtained,_as illustrated in_FIG. 21B. This_example shows that the_current falls to_zero_about 60 nanoseconds (nsecs) after the transistor Q101 is turned off.
In this constant current_source,_the load_resistor_R100_acts as a current-limiting load;_therefore, the characteristics obtained when_the current_rises are slower than the characteristics obtained when_the_current falls. FIG._21A illustrates an example of a time change in_the current when the current rises._This example shows_the_current_reaches a constant current_about 2.8 μsec after the transistor_Q101 is turned on.
If the difference_between the current values obtained before and_after the current is changed is_100%, the time it takes_to change_from 10% to 90% when_the current rises_is referred_to as the_rise transition time. Similarly, if the_difference between the_current values obtained before and after_the_current is changed_is_100%,_the time_it takes to_change_from 90%_to_10% when the current falls is_referred_to as the fall transition time.
FIG. 22_illustrates an example of_the_light emission behavior obtained_when the white LED that_has the characteristics illustrated in FIGS._18A and_18B are_driven by using a constant current source that has the characteristics_illustrated in FIGS. 21A and 21B._The drive current slowly_rises, and_the_emission by the_yellow_fluorescent material_in the white LED slowly responds to_the drive_current. Therefore, during the rise transition_time, the blue LED_and_the yellow fluorescent material in the_white LED enter a light-on state_over the same period of_time_(the_period A in FIG. 22).
Conversely,_during the fall transition time, as_the blue LED_has superior emission response characteristics with respect_to_the drive current, the blue LED_enters_a light-off state at almost the_same_time_as the drive current is_changed. However, the yellow fluorescent material_has inferior emission response characteristics with respect to the_drive current as_compared to the blue LED;_therefore,_it_takes time to follow a change in the drive current_(the period_B in FIG._22). During the fall transition time, a state occurs in_which, although the blue LED has already_entered a light-off state, the yellow fluorescent material still emits light_(residual light), which is illustrated as the area_Ye in FIG. 22. In a state_where there is residual_light_from the yellow fluorescent material, the white_LED_emits_light_of a different_color (yellow