Fuji Power MOSFET Power calculation method

Transcription

1 Fuji Power MOSFE Power clculi mehod Design ool Cher. Overview is necessry o check wheher he ower loss hs no exceeded he Asolue Mximum Rings for using MOSFE. Since he MOSFE loss cnno e mesured using ower meer, i is required o clcule i from drin-source volge nd drin curren D wvefo oined y using device such s n oscilloscoe. his documen rovides he mehod o clcule he MOSFE loss. n ddii, how o use he loss-clculi ssisnce ool is rovided. Cher. Clculing elecric energy [] Generlly, he elecric energy [] for eriod - s indiced in Figure cn e clculed y he inegri of volge imes curren s indiced in he following formul: V ( ) ( ) d() While, () nd V() cn e exressed s follows: V() V V V ( ) + V ( ) ( ) + (3 ) V () Figure : Volge V() nd curren () for eriod - V hus, inegre hem for he ime eriod of - o oin he following elecric energy []: 3 ) ( ) ( ) ) ( ) ( ) ( ) V + V ( ) (4 ) By using he ove formul nd rirrily sering he eriod -, you cn even oin he elecric energy [] for nliner wvefo. Cher 3. Clculing elecric energy [] from volge nd curren wvefo o clcule he ower loss from volge nd curren wvefo for he eriod, divide ino rnges where liner roximi cn e lied, s indiced in Figure. OFF ON ON ON OFF OFF D Figure : Exmle of loss clculi wvefo n Figure, he curren wveform sloe chnges during MOSFE is eing urned off. herefore, o clcule he loss from wvefo of Figure, divide ino,,..., 5. n cul circuis h include rsiic ccince of MOSFE, he volge nd curren chnge exenilly during rnsii eween nd off. Becuse i is difficul o exenilly reresen volge nd curren from he oserved wvefo device such s oscilloscoe, liner roximis re used. Dec D_Power clculi mehod Rev. E /7 Fuji Elecric Co., d. All righs reserved.

2 Fuji Power MOSFE Design ool Cher 4. Clculing elecric ower [W] from elecric energy [] As indiced in Figure 3, red he volge nd curren vlues of wveform for he eriod. Use he red vlues nd formul (4) o clcule he loss. V V 3 3 V D /f Figure 3: Red volge nd curren vlues from wveform exmle By clculing he loss for ech of he secis [s] o 5 [s], he loss for ech of he secis [] o 5 [] cn e derived. Since MOSFE is elecriclly cducing in he seci [s], he volge is roduc of he MOSFE's ON-resisnce R ON nd he curren. Formul (5) o (9) show exressis for ech of he secis. he eriod [s] is lso inverse of frequency f [Hz], herefore he ower P [W] csumed y MOSFE cn e oined from formul (). Noe h he following formuls re simlified o he finl fo sed he volge nd curren sloes nd zero-cross. Formuls for ech ern re shown in Aendix le. V Sulemenry informi <Effecive vlue curren> (5 ) RON 3 ( ) ( ) + ( ) V ( + ) (7 ) ( V + V ) (8 ) (9 ) ( ) f ( ) P Formul () is used o oin elecric energy [] ON-resisnce R ON. n he ON-eriod, ower [W] cn e oined from effecive vlues. Using [ s he effecive curren in he seci, he ower P [W] in he ON-eriod cn e exressed y formul () from formul (). P RON RON 3 ( ) ( ) + () n he ON-eriod, MOSFE will csume he ower h is he roduc of ON-resisnce R ON nd squre of effecive curren. herefore, he ower increses qudriclly deending he increse of he curren vlue. Formul o clcule he effecive curren vries deending he curren wveform. Aendix le shows yicl wvefo nd formuls o clcule effecive vlues. Dec D_Power clculi mehod Rev. E /7 Fuji Elecric Co., d. All righs reserved.

3 Fuji Power MOSFE Design ool Cher 5. Clculing loss from wveform Acul oering wvefo re used for loss clculi exmle. For clculi from oering wvefo, check h he wve cycle is cler, he urn-on nd urn-off volges nd curren cn e red, nd he curren vlues cn e red in he ON-eriod. he followings show cully mesured wvefo nd red vlues. Check he ON-resisnce R ON in he d shee for MOSFE h you re using. (he following clculi uses he mx vlue ch 5, which is red from chr in he d shee.) : 7.5us Mesuremen oins Device ye Ouu ower Flyck-Cverer of he swiching MOSFE FMVN38S (V/8.A/R DS()@5 mx.94[ω]) 5W (DC:9V/3.4A) urn - OFF V/div ime 5us/div D.5A/div urn - ON No loss for urn - ON. ime ns/div D V/div.5A/div ime ns/div Z Z 3 Z 4 Z D V/div.5A/div ON eriod ON : 3.9us :.A Mesured vlues V V urn - ON us V V A A ON eriod 3.9us V V A.A Z 3ns V 4V.A.A V/div urn - OFF Z 35ns 4V 4V.A.5A Z 3 ns 4V 37V.5A.7A ime 5ns/div D.5A/div Z 4 5ns 37V 385V.7A A he red vlues re used for he loss clculi. he followings re he clculi resuls wih he resecive vlues ssigned o he formul (4). urn ON : [ ] ON eriod :. 94[ Ω]. [ 3. 9[ us] 4. 89[ u 3 Z : 3 4[ V ]. [ 3[. [ u] ( ) ] Z : 4 53 u 3 ( 38[ V ]. ) + ( 38[ V ]. [ ) (. 4[ V ]) + 4[ V ]. [ 3 3. [ ] Z3 : 5 7 u ( V ]. 8[ ) ( V ]. ) (. 8[ 4[ V ]) + 4[ V ]. [ 8. [ ] Z4 : 8 u 3 ( V ]. ) + ( V ]. ) (. 3 V ]) + 3 V ]. 3. [ ] From he following clculi resuls, he MOSFE loss P [W] h cn e clculed from wvefo is.8 [W]. [ ] [ u] +. [ u] [ u] + 8. u] [ u] P. 8[ W ] 7. us] Dec D_Power clculi mehod Rev. E 3 /7 Fuji Elecric Co., d. All righs reserved.

4 Fuji Power MOSFE Design ool Cher. Using MOSFE ower clculi ool (Excel) he loss clculi mehods descried ove re ll inended for mnul clculi. n his seci, Excel is used. his Excel file is designed o e used for he loss clculi nd chnnel emerure clculi. he file cins shee h descries how o use he ool. Plese check he cen efore using i. Seci Downlod he Excel file from he Fuji Elecric's home ge: UR h:// Home > Producs & Soluis > Power Semicducors > Produc nformi > Power MOSFE > Design ools < File nme > Power clculi ool_rev E.xlsx Seci Oen he downloded file, Power clculi ool_rev E.xlsx, nd click he "clculi" shee. Seci 3 nu required vlues from he oined wvefo nd he d shee of MOSFE h you re using. Use he oined wvefo in Cher 5 nd MOSFE d shee for comring he clculi. [C] nu he model of MOSFE h you re using. his cell is oil; clculi is no ffeced if i is emy. [C4, C5] Red nd inu he ON-resisnce from he Drin-Source On-se resisnce chr in he MOSFE d shee. he C5 cell is inended for MEMO. Use i o record he d such s chnnel emerure. [C] nu he swiching cycle in n [us] uni from wvefo. [F column] You cn inu volges nd currens in he OFF-eriod; however, hose d cn e omied ecuse he clculi resul is zero. he OFF-ime cn lso e omied ecuse here will e shown he difference eween he vlue inu in C nd vlues inu for urn- ON, ON-eriod nd urn-off. [G o N colum nu he red vlues of wvefo in he urn-on ime, volge nd curren vlues. n he wvefo for his documen, no d is inu since here is no inerseci of volge nd curren. [O o X colum nu he red vlues of wvefo in he ON-eriod ime nd curren vlues. For volges in he ON-eriod, roduc of R ON nd curren vlue is shown s he clculi resul. [Y o AF colum nu he red vlues of wvefo in he urn-off ime, volge nd curren vlues. nu hose vlues, nd you will see.8w in C9 s he resul of he loss clculi. he resul is he sme s hose oined when he loss clculi is mnully execued. Dec D_Power clculi mehod Rev. E 4 /7 Fuji Elecric Co., d. All righs reserved.

5 Fuji Power MOSFE Design ool Annex le Volge cdii Curren cdii Wveform Clculi formul V <V < V() V V () f : V : V f : : ) ( ) ) ( ) ( + ) ( V + V ) V + V V <V V() () V V ( V + V ) f : V : V V <V > V() () V V f : V : V f : : ) ( ) ) ( ) ( + ) ( V + V ) V + V V V < V() () V V V ( + ) f : : V V() V V V V () V V V > V() () V V V ( + ) f : : V V >V < V() () V V f : V : V f : : ) ( ) ) ( ) ( + ) ( V + V ) V + V V >V V() () V V ( V + V ) f : V : V V >V > V() () V V f : V : V f : : ) ( ) ) ( ) ( + ) ( V + V ) V + V Dec D_Power clculi mehod Rev. E 5 /7 Fuji Elecric Co., d. All righs reserved.

6 Fuji Power MOSFE Design ool Annex le Wveform Effecive vlue Averge vlue ( sin ) ω d vg π sinωd d vg d 3 + ( ) + ( ) d + vg ( + ) + d 3 d vg d Effecive vlue of synhesized wve Effecive vlue of synhesized wve cn e oined y squre roo of sum of squres of effecive vlues for ech eriod d + 3 d Dec D_Power clculi mehod Rev. E /7 Fuji Elecric Co., d. All righs reserved.

7 Fuji Power MOSFE Design ool Noe. he cen of his documen (roduc secificis, chrcerisics, d, merils, srucure, ec.) is sed he d s of Decemer,. he roducs descried in his documen re sujec o chnge wihou rior noice due o revised secificis or for oher res. f you use ny of he roducs descried in his documen, lese ge he les versi of he secificis nd check he d efore using i.. he clculi resuls h you oin vi he mehod descried in his meril should e used ly s n indici. he clculi resuls (vlues) oined using his meril do no ssure he Fuji Elecric Co. roducs nd is oeris. 3. f you need o rerin or coy ll or ori of his documen, you need wrien csen from Fuji Elecric Co. he cen of his documen is sujec o chnge wihou noice due o imrovemen or for oher res. he lici exmles or r csns descried in his documen re inended s n id of design. he vrii in rs or usge cdiis re no sufficienly csidered. When using i, lese csider vrii in rs, usge cdiis or oher fcors for design. Dec D_Power clculi mehod Rev. E 7 /7 Fuji Elecric Co., d. All righs reserved.