PresentationAgendaIntroductionDC-to-DC converter enables the transformer to be small.- Throughout the design transformer, the core size, optimum induction is selected and the primary turns, secondary turns are calculated.Forward & Half bridge conv.: Vo= VdDFigure 1 - Forward converterFigure 2 - Half bridge forward converterTHE STEPS FOR TRANSFORMER DESIGNEXAMPLE FOR TRANFORMER DESIGNTotal = 98WTsw= = 33s ton = = 16.5 sDifferenceParameterPresentationStudent: Phi Nguyen (3631)Date: 12/06/20031TRANSFORMER DESIGN FOR FORWARD CONVERTER AND HALF BRIDGE FORWARDCONVERTERAgenda1) Introduction2) Circuit Illumination of DC to DC3) Steps for Transformer design4) Example for Transformer design Forward Converter Half Bridge Converter(optional)5) Advantage26) Conclusion7) QuestionIntroduction- Transformer has two basic functions: toprovide electrical isolation and step up or stepdown time varying voltage and current.- DC-to-DC converter enables the transformerto be small.- It can provide multiple output voltage.- Throughout the design transformer, the coresize, optimum induction is selected and theprimary turns, secondary turns are calculated.3CIRCUIT ILUMINATION OF DC-TO-DC FORWARD ANDHALF BRIDGE CONVERTER In general, the transformer for the half bridge converter follows thesame general principal used for the forward converter.Buck dc-dc converter: Vo=VdD Forward & Half bridge conv.: Vo= Vd12NND Figure 1 - Forward converterN1N3 N2LmVdD1D2D3C1VoS1L1Figure 2 - Half bridge forward converter4S1S2VdC1C2N1N2N2'D1D2CVoLxTHE STEPS FOR TRANSFORMER DESIGNStep 1: Selecting core size.From the basic of transmitted power andthe manufacture’s recommendation.(Figure 2.2.2)Step 2: Selecting optimum induction.Use manufacture’s published chart.(Figure 2.9.1)Step 3: Calculate primary turns. Step 4: Calculate secondary turns. 2121NNVV 5Note: Maximum duty ratio: Dmax= 0.5 (ton=toff).EXAMPLE FOR TRANFORMER DESIGN* Forward converter:P = 100W at fsw 30 kHz.Input: Vi = 90 – 130 V (nominal 110V) 50-60Hz.Output Vo and Io :5V at 10 A (50W)+12V at 2A (24W)-12V at 2A (24W)Total = 98W-Core size: Use figure 2.2.2At 100W  E 42-15. Core parameters: area Ae=181 mm2-Optimum induction: Use figure 2.9.1 At 100W and f = 30kHz.  Bopt=150mT (for push pull).6.  Bm=250mT (for forward conv.)-Calculate primary turns:Tsw= swf1 = 33s  ton = 2Tsw = 16.5 s-Calculate primary voltage (V1):Use the approximate conversion factor:V1 = Vi x (1.3) x (1.9)V1 = 110 x (1.3) x (1.9) = 272VMin. primary turns:Nmin = )2(mm A . (T) B).( t. (V)Vemon1 s = 100 turnsAt V1 min = 90V in dc primary voltageV1min= 90 x (1.3) x (1.9) = 222 VV/turn = minmin1NV =100222 = 2.22 V/turn7-Calculate secondary turns:N2D2CVoLxV2 Figure 3 - Single output applicationVo = V2 x Dmax  V2 = maxDVo = 10V.Choose V2 = 12V (2V drop D1 and Lx)N2min =22.212 = 5.4 turns. Choose N2 = 5.5 turns.221min1NVNVN1=V1min22VN = 102 turns.Similarly, we have:V2 (at 12V) = 2 V0 + Vdrop = 26 V  N2 (at 12V) = 11.9 turns. Choose N2 (at 12V) = 12 turns8(Confirm the result by Pexpt) DifferenceParameter Calculation PExpt % DifferenceV1(V) 110 110 /V2(V) 12 13.6 11.7%N1(turn) 102 100 2%N2(turn) 5.4 5.0 8%9*Half bridge Forward converter:This design is very similar to the method use forthe forward converter example.Figure 2.11.1 - Typical core section graphP = 100W at fs50 kHz. Vi = 85 – 137 V (nominal 110V). Vo = 5V and Io = 20 A (100W).V1 = Vi x (1.3) x (1.9) V1min = 85 x (1.3) x (1.9) = 209VV1nominal = 110 x (1.3) x (1.9) = 272VV1max = 137 x (1.3) x (1.9) = 338V-Core size: Use figure 2.11.1, at 100W .We choose core type EC 41. Core parameter: core area Ae=120 mm2-Optimum induction: Use figure 2.9.1 at 100Wand f=50kHz. Bopt= 85 mT ( for P.P )For half bridge, we choose the max. flux densityBm=210mT.[ Bm = (85 x 2) . nomVV1max1 = 210mT ]10Figure 4 - Multiple output applicationN21D3D4C2L2N22D5D6C3L3N2D1D2C1L1+12v-12VCOMMON+5vN111CORE CONSIDERATION:Related formulas: Vd = N1 dtd ; Vd = N1 ontmax max = 2Bmax Ae = 1on dN t.V (Bmax = 2B)Bmax = sw . e . 1dfA4NV (ton = swfD ; D = 0.5)For forward converter:Bmax < 0.5 (Bm – Br) Bm = Bsat-A large value of Bm allows Bmax largeresult to smaller Ae. Therefore, smallercore size.-Higher switching frequency result insmaller core size.(However fsw> 100kHz result in a smaller valueof Bmax to be chosen to limit the core losses).Advantage12- Isolate the output from the input electrically.- Smaller core size.- Provide a multiple output voltage.- Low cost. The design for the DC power supplies isvery necessary. *ConclusionTransformer is designed in almost AC to DCand DC-DC converter. It is an importantdevice in the DC power supply. Specially,in dc-dc converter, transformer has a smallsize and therefore a low cost.13CONCLUSION:Transformer is designed in almost AC toDC and DC-DC converter. It is animportant device in the DC power supply.Specially, in dc-dc converter, transformerhas a small size and therefore a low cost.14A list of References:1- “Switch mode power supply handbook” by Keith Billing, 2ndEdition. Mc Graw Hill, 1999.2- “Power Electrics: Converter, Application and Design”, Mohan,Undeland and Robbin, Willey, 1989.3- “Introduction to Power Electronic” by Daniel W. Hart, PrenticeHall, Inc. 1997.4- Lecture note “Power Electric” by Prof. D. Zhou, Ph. D. (2003).5-