(Flyback Transformer Design Theory)

*

*

*

*

*

. .

(Flyback)"Buck-Boost".

..

:

1. ,,

.

2. ,.

3. .

4. ,, 85~265V

..

:

1. ,,,150W

.

2. (CCM),,,

,.

3. ,CCM / DCM,,

,.

.

1(The isolated flyback converter), " T "

." T "Transformer- choke.:

Tr ton,Np Ip,(E = LpIp / 2).NpNs

,D,.Tr off , :

(e = -N/T),,D,IL

.2.

, tonIpVce:

Vce max = VIN / 1-Dmax

VIN: ; Dmax :

Dmax = ton / T

(Flyback Transformer Design Theory)

1124182443 1/12 Lisc Oct.

,,Dmax,Dmax0.5,

Dmax = 0.4,Vcemax 2.2VIN.

Tr onIe,Ip: Ic = Ip = IL / n. IL = Io,Io

, nIc,, NpIp = NsIs

. Ip:

I c = Ip = 2Po / (*VIN*Dmax) :

:

: Po = LIp2 / 2T

: VIN = Ldi / dt di = Ip, 1 / dt = f / Dmax,:

VIN = LIpf / Dmax Lp = VIN*Dmax / Ipf

Po :

Po = VINf DmaxIp2 / 2f Ip = 1/2VINDmaxIp

Ip = 2Po / VINDmax

:

VIN : (V) Dmax : 2

Lp : (mH) Ip : (A)

f : (KHZ)

,,

,.

:

1. DCM (Discontinuous Inductor Current Mode) " ": ton

(toff).

2. CCM ( Continuous Inductor Current Mode) " " :

toffton.

DCMCCM,3.,VIN

, IL,.

DCM / CCM..DCM /

CCM.,PWM.DCM,

CCM.

CCM " ".

1124182443 2 / 12 Lisc Oct.

() DCM Waveforms ( ) CCM Waveforms

3 DCM / CCM

,ton"toff",.

,

= VIN ton / Np = Vs*toff / Ns

//.

3DCMCCM:DCMTr ton,

,Lp,Ip

(winding lose),

,.

CCM,,ton.

.CCM,Lp,

DCM,.

,DCMCCM,

( CCM Ip = Imax - Imin ).

( a )

( b )

( a )

I

t

I

t

II

t

t

Full LoadHigh VIN

Mode BoundaryLow VIN

( b )

1124182443 3 / 12 Lisc Oct.

FLYBACK TANSFORMER DESIGN

FLYBACK:

1. . CCM,,AIR GAP, H

,,.

P = f*VeBs H d B Ve: .

or P = 1/2Lp (Imax2 - Imin

2)

Imax, Imin ,.

,B.HAIR

GAP,4.

4

Bac,Hac,,

CORE.

COREHDC,BDC,

,.

CCM,,.

,BBac; ,

HHDC. BacHac.,Hac. ,

.

Br

Bs

H

B

Bac

HDC2Core

BDC

Bs

1124182443 4/12 Lisc Oct

2. . CORE,(),,,

,,.

AP. CORE

,,.

3. ,.,

. ,

ton,. D0.5. DCM.

: Lp,,ton(50%),"" ,

,. .

AIR GAPLp,.

4. Lp . Lp. Lp.

. Lp. Lp

,CCM,. DCM,AIR GAP,Lp

,,.

(DCM / CCM) . DCM,

. Tr,DC,

(I2R). CCM,,,

.

,,. ,

,,.

5. . ,VINmaxIomin,Io,

. ,VINmaxDmax,

,,. ,:

(VINmax),(Dmax). B,

,.

1124182443 5 / 12 Lisc Oct.

Flyback Transformer Design Example . :

step0 SPEC: VIN , fs , Vo , Io , D, , t , CCM&DCM , Load .

step1 CORE,B.

step2 CORE SIZETYPE.

step3 IOB

step4 ,CHECK Dmax.

step5 DCM / CCMISB.

step6 (Lp&Ls).

step7 CCMIsp.

step8 CCMIpp.

step9 Np, Ns .

step11 ,.

step12 .

step13 .

step14 SAMPLE,.

step15 DQ.

( DESIGN EXAMPLE I )

Step0. (Specification)

: 60watts ADAPTER POWER MAIN X'FMR

INPUT : 90 ~ 264 Vac 47 ~ 63 HZ ; 4.

OUTPUT : DC 19V 0 ~ 3.16A ; Vcc = 12 VDC 0.1A

0.83 ; f s = 70KHZ ; Duty cylce over 50%

t 40o () @ 60W ; X'FMR 21mm.

CASE Surface Temperature 78 .

Note : Constant Voltage & Current Design (UC3843AD)

Step1. CORE,B

ADAPTER DESIGN,,COREBs,

i,,Ferrite Core, TDK PC40 or PC44, TDK DATA

BOOK, PC44PcvPC40 , PC44.

1124182443 7 / 12 Lisc Oct.

(Transformer Design Procedure)

CORE Bs

CORE Ap = AwAe = (Pt*104) / 2B*f *J*Ku

CCM / DCM

n = VIN(min) / (Vo+Vf)*[Dmax / (1-Dmax)]

Ipp = Isp / n ; Isp = ISB + Is

Lp = n

2Ls ; Ls = (Vo + Vf)*(1-Dmax)Ts / ISBISB = 2IOB / (1-Dmax)

Np = Lp*Ipp / (B*Ae) ; Ns = Np / n

AIR GAP lg = 0.4*Lp*Ipp / (B*Ae) = Np2*o*Ae / Lp

dw = (4AW / )

.

1124182443 6 / 12 Lisc Oct.

:

i = 2400 25% Pvc = 300KW / m2 @100KHZ ,100

Bs = 390mT Br = 60mT @ 100 Tc = 215

X'FMR, B.

B = 60%Bm, B = 0.6 * (390 - 60) = 198mT 0.2 T

Step2 Core Size Type.

1> core AP size

AP= AW*Ae=(Pt*104)/(2B*fs*J*Ku)

= [(60/0.83+60)*104]/(2*0.2*70*103*400*0.2) = 0.59cm4

Pt = Po / +Po

J : A / cm2 (300~500)

Ku: 0.2 ~ 0.5 .

2> .

,BOBBIN, EMI,AP

, , TDKDATA BOOK,RM10, LP32/13, EPC30

,RM10EPC30LP32/13,LP32/13 PC44,:

Ae = 70.3 mm2 Aw = 125.3mm2 AL = 263025% le = 64.0mm

AP = 0.88 cm4 Ve = 4498mm3 Pt = 164W ( forward )

Step3 IOB ( DCM / CCM BOUNDARY )

IL80% Iomax.

: IOB = 80%*Io(max) = 0.8*3.16 = 2.528 A

Step4 n

n = [VIN(min) / (Vo + Vf)] * [Dmax / (1-Dmax)] VIN(min) = 90*2 - 20 = 107V

= [107 / (19 + 0.6)] *[0.5 / (1- 0.5)]

= 5.5 6

n 5 6, 6 ,. CHECK Dmax

Dmax = n (Vo +Vf) / [VINmin + n (Vo + Vf)]

= 6*(19 + 0.6) /[107 + 6*(19 + 0.6)] = 0.52

1124182443 8 / 12 Lisc Oct.

Step5 CCM / DCMISB.

ISB = 2IOB / (1-Dmax) = 2*2.528 / (1-0.52) = 10.533

Step6 Ls Lp.

Ls = (Vo + Vf)(1-Dmax) * Ts / ISB

= (19+0.6) * (1-0.52) * (1/70000) / 10.533 = 12.76 uH

Lp = n2 Ls = 62 * 12.76 = 459.4 uH 460 uH

,CCM,,DCM

.

Step7 CCMIsp.

Io(max) = (2Is + ISB) * (1- Dmax) / 2

Is = Io(max) / (1-Dmax) - (ISB / 2 )

Isp = ISB +Is = Io(max) / (1-Dmax) + (ISB / 2 )

= 3.16 / (1-0.52) + 10.533 / 2 = 11.85A

Step8 CCMIpp.

Ipp = Icp / n = 11.85 / 6 = 1.975 A

Step9 NpNs .

1> Np Np = Lp * Ipp / (B* Ae)

= 460*1.975 / (0.2*70.3) = 64.6 Ts

,,

, Np = 60Ts OR Np = 66Ts

n,,PfePcu, Np = 60 Ts.

2> Ns Ns = Np / n = 60 / 6 = 10 Ts

3> Nvcc

Va Va = (Vo + Vf) / Ns = (19+0.6) / 10 = 1.96 V/Ts

Nvcc = (Vcc + Vf) / Va = (12+1) / 1.96 = 6.6 7 Ts

Step10 AIR GAP .

lg = Np2*o*Ae / Lp = 60

2*4*3.14*10-7*70.3 / 0.46 = 0.69 mm

I

t

I

t

1124182443 9 / 12 Lisc Oct.

Step11 dw,.

1> dwp

Awp = Iprms / J Iprms = Po / / VIN(min) = 60/0.83/107 = 0.676A

Awp = 0.676 / 4 J4A / mm2 or 5A / mm2

= 0.169mm2 0.35mm*2

2> dws

Aws = Io / J = 3.16 / 4 = 0.79 mm2 1.0 mm

,,0.4, 0.4Aw= 0.126mm2,

0.79 / 0.126 = 6.27 6

Ns0.4 * 6 .

3> dwvcc

Awvcc = Iv / J = 0.1 / 4 = 0.025mm2 0.18mm

4A / mm2,,,J.

4> .

0.4Aw Np*rp*(1/2dwp)2 + Ns*rs*(1/2dws)

2 + Nvcc*rv*(1/2dwv)2

0.4Aw 60*2*3.14*(0.35/2)2+10*6*3.14+(0.4/2)2+7*3.14*(0.18/2)2

11.54 + 7.54 + 0.178 = 19.26

0.4 * 125.3 = 50.12

50.12 > 19.26 OK

Step12 .

1> .

2> RDCRac @100

3>

4> (Total)

: Np = 60Ts , LP32/13BOBBIN 4.33cm

lNP = 60*4.33 = 259.8 cm

Ns = 10Ts

lNS = 10*4.33 = 43.3 cm

1124182443 10 / 12 Lisc Oct.

Nvcc = 7Ts

lNvc = 7 * 4.33 = 30.31cm

: 0.35mm WIRE RDC = 0.00268/cm @ 100

0.40mm WIRE RDC = 0.00203 /cm @ 100

0.18mm WIRE RDC = 0.0106 /cm @ 100

R@100 = 1.4*R@20

. Io = 3.16A.

: Ispa = Io / (1-Dmax ) = 3.16 / (1- 0.52) = 6.583A

: Isrms = (1-Dmax)*I2spa = (1- 0.52)*6.583

2 = 4.56A

: Isac = (I2srms - Io

2) = (4.562-3.162) = 3.29A

:

Np*Ip = Ns*Is

: Ippa = Ispa / n = 6.58 / 6 = 1.097A

: Iprms = Dmax * Ippa = 1.097 * 0.52 = 0.57A

: Ipac = D*I2ppa = 1.097*0.52 = 0.79A

.

: RPDC = ( lNp * 0.00268 ) / 2 = 0.348

Rpac = 1.6RPDC = 0.557

: RSDC = ( lNS*0.00203 ) /6 = 0.0146

Rsac = 1.6RSDC = 0.0243

Vcc : RDC =30.31*0.0106 = 0.321

:

: PSDC = Io2RSDC = 3.16

2 * 0.0146 = 0.146W

: Psac = I2sac*Rsac = 3.292*0.0234 = 0.253W

Total : Ps = 0.146 + 0.253 = 0.399 W

: PPDC = Irms2RPDC = 0.57

2 * 0.348 = 0.113W

: Ppac = I2pac*Rpac = 0.79

2*0.557 = 0.348W

Vcc() Total Pp = 0.461W

: Pcu = Pc + Pp = 0.399 + 0.461 = 0.86 W

1124182443 11 /12 Lisc Oct.

2> PFe

TDK DATA BOOKPC44B = 0.2T ,Pv = 0.025W / cm2

LP32 / 13Ve = 4.498cm3

PFe = Pv * Ve = 0.025 * 4.498 = 0.112W

3> Ptotal = Pcu + PFe = 0.6 + 0.112 = 0.972 W

4> t

t = 23.5P/Ap = 23.5 * 0.972 / 0.88 = 24.3

tSPEC,OK.

Step13

LP32 / 13 BOBBIN 21.8mm.

6.4mm.

LK,, :

X'FMR :

Np #1 3.2 / 3.2 2 -- A 0.35 * 2 30 1L

SHI #2 3.2 / 3.2 SHI- 4 2mils * 12 1 3L

Ns #3 3.2 / 3.2 8.9 - 6.7 0.4 * 6 10 3L

SHI #4 3.2 / 3.2 SHI- 4 2mils * 12 1 1L

Np #5 3.2 / 3.2 A -- 1 0.35 * 2 30 1L

Nvcc #6 3.2 / 3.2 3 -- 4 0.18 7 2L

#7 A 2L

1124182443 12 / 12 Lisc Oct.

(JIS 0123)

0 1 2 3

/ km / km kg / km(mm) (mm2 ) (mm) (mm) (mm) ( 20 ) (mm) (mm) (mm) (mm) ( 20 ) (mm)

0.04 0.0013 0.03 0.056 0.002 0.052 15670 0.01153 0.040.05 0.0020 0.04 0.069 0.003 0.064 10240 0.01745 0.050.06 0.0028 0.04 0.081 0.003 0.075 6966 0.02595 0.060.07 0.0038 0.04 0.091 0.003 0.085 4990 0.035 0.070.08 0.0050 0.05 0.103 0.003 0.097 3778 0.046 0.080.09 0.0064 0.05 0.113 0.003 0.107 2959 0.058 0.090.10 0.0079 0.156 0.009 0.140 2647 0.05 0.125 0.003 0.118 2381 0.0698 0.10.11 0.0095 0.166 0.009 0.150 2153 0.05 0.135 0.003 0.128 1957 0.087 0.110.12 0.0113 0.180 0.010 0.162 1786 0.06 0.147 0.004 0.139 1636 0.1006 0.120.13 0.0133 0.190 0.010 0.172 1505 0.06 0.157 0.004 0.149 1389 0.130.14 0.0154 0.200 0.010 0.182 1286 0.06 0.167 0.004 0.159 1193 0.1368 0.140.15 0.0177 0.210 0.010 0.192 1111 0.06 0.177 0.004 0.169 1037 0.150.16 0.0201 0.222 0.011 0.204 969.5 0.07 0.189 0.005 0.181 908.8 0.1788 0.160.17 0.0227 0.232 0.011 0.214 853.5 0.07 0.199 0.005 0.191 803.2 0.170.18 0.0254 0.246 0.012 0.226 757.2 0.08 0.211 0.005 0.202 715 0.2263 0.180.19 0.0284 0.256 0.012 0.236 676.2 0.08 0.221 0.005 0.212 640.6 0.190.20 0.0314 0.266 0.012 0.246 607.6 0.08 0.231 0.005 0.222 577.2 0.2793 0.20.21 0.0346 0.276 0.012 0.256 549 0.08 0.241 0.005 0.232 522.8 0.210.22 0.0380 0.286 0.012 0.266 498.4 0.08 0.252 0.005 0.243 480.1 0.220.23 0.0415 0.298 0.013 .0.278 454.5 0.09 0.264 0.006 0.255 438.6 0.3694 0.230.24 0.0452 0.308 0.013 0.288 416.2 0.09 0.274 0.006 0.265 402.2 0.240.25 0.0491 0.318 0.013 0.298 382.5 0.09 0.284 0.006 0.275 370.2 0.250.26 0.0531 0.330 0.013 0.310 358.4 0.09 0.294 0.006 0.285 341.8 0.472 0.260.27 0.0573 0.340 0.013 0.320 331.4 0.09 0.304 0.006 0.295 316.6 0.270.28 0.0616 0.350 0.013 0.330 307.3 0.09 0.314 0.006 0.305 294.1 0.280.29 0.0661 0.360 0.013 0.340 285.7 0.09 0.324 0.006 0.315 273.9 0.5872 0.290.30 0.0707 0.374 0.014 0.352 262.9 0.01 0.337 0.007 0.327 254 0.6435 0.30.32 0.0804 0.394 0.014 0.372 230 0.01 0.357 0.007 0.347 222.8 0.7194 0.320.35 0.0962 0.424 0.014 0.402 191.2 0.01 0.387 0.007 0.377 185.7 0.8553 0.350.37 0.1075 0.446 0.014 0.424 170.6 0.01 0.407 0.007 0.397 165.9 0.370.40 0.1257 0.480 0.015 0.456 145.3 0.011 0.439 0.007 0.429 141.7 1.118 0.40.45 0.1590 0.532 0.016 0.508 114.2 0.011 0.49 0.007 0.479 112.1 1.414 0.450.50 0.1963 0.586 0.017 0.560 91.43 0.012 0.542 0.008 0.531 89.95 1.745 0.50.55 0.2376 0.646 0.017 0.620 78.15 0.012 0.592 0.008 0.581 74.18 2.112 0.550.60 0.2827 0.698 0.017 0.672 65.26 0.012 0.644 0.008 0.632 62.64 2.513 0.60.65 0.3318 0.752 0.018 0.724 55.31 0.012 0.694 53.26 2.95 0.650.70 0.3848 0.804 0.019 0.776 47.47 0.013 0.746 45.84 3.421 0.70.75 0.4418 0.860 0.020 0.830 41.19 0.014 0.798 39.87 0.750.80 0.5027 0.914 0.021 0.882 36.08 0.015 0.852 35.17 4.469 0.80.85 0.5675 0.966 0.022 0.934 31.87 0.015 0.904 31.11 0.850.90 0.6362 1.020 0.023 0.986 28.35 0.016 0.956 27.71 5.656 0.90.95 0.7088 1.072 0.024 1.038 25.38 0.017 1.008 24.84 0.951.00 0.7854 1.138 0.025 1.102 23.33 0.017 1.062 22.49 6.982 11.10 0.9503 1.242 0.026 1.204 19.17 1.11.20 1.1310 1.342 0.026 1.304 16.04 10.06 1.21.30 1.3273 1.448 0.027 1.408 13.61 1.31.40 1.5394 1.548 0.027 1.508 11.7 13.68 1.41.50 1.7671 1.654 0.028 1.612 10.16 1.51.60 2.0106 1.754 0.028 1.712 8.906 17.88 1.61.70 2.2698 1.856 0.029 1.814 7.781 1.71.80 2.5447 1.956 0.029 1.914 7.007 22.63 1.81.90 2.8353 2.062 0.030 2.018 6.278 1.92.00 3.1416 2.162 0.030 2.118 5.656 27.93 22.10 3.4636 2.266 0.031 2.220 5.123 31 2.12.20 3.8013 2.368 0.032 2.322 4.662 2.22.30 4.1548 2.460 0.032 2.422 4.26 36.94 2.32.40 4.5239 2.574 0.033 2.562 3.908 2.42.50 4.9087 2.678 0.034 2.682 3.598 2.52.60 5.3093 2.778 0.034 2.728 3.324 47.29 2.62.70 5.7256 2.878 0.034 2.828 3.079 2.72.80 6.1575 2.978 0.034 2.982 2.861 2.82.90 6.6052 3.078 0.034 3.028 2.665 58.72 2.93.00 7.0686 3.178 0.034 3.128 2.489 64.76 33.20 8.0425 3.388 0.034 3.338 2.198 71.49 3.2

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