Jeffrey HwangWinning by Power

Alland Chee, Elvis Lin, Joe Wong

and

Jeffrey H. Hwang

Design a 100WPFC Boost Inductor

Jeffrey HwangWinning by Power

Criteria of Selection

Size

Efficiency

Cost

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• R=S: [ ] Magnetic Reluctance=The resistance of a material to a magnetic field

• Φ: [Weber] Magnetic Flux=A measure of quantity of magnetism.

• B: [Tesla]=[ Gauss] Magnetic Field=Flux Density=Magnetic Induction

• H: [ ] Magnetic Field Strength=Magnetic Force=MMF per length

Review Important Magnetic Variablesand

Important Magnetic Constants

• • 1[Tesla]=1[Weber/Meter2]=104

[Gauss]=1[Newton/(Ampere x Meter)]

• 1[Weber]=1[Wb]=108Maxwell• [L]=1[henry]=1[Volt x

Sec/Ampere]=1[Wb/Amp]• μ0=Air Permeability

Constant=4π x 10-7 [Tesla Meter/Ampere]

weber

turnampere

410

Meter

TurnAmpere

][0125.0][004.0 OeOeMeter

TurnAmpere

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• R=mmf /ΦB=NI/ΦB=

ιm/(Ac μ)

• Re=Rl + Rair=

ιm/(Ac μ) + ιair/(Ac μair)=

• ΦB=

• L=N ΦB/I=N2/Re=

Important Magnetic Formula

• B=μ H= μ x mmf/leff=

ΦB/Ac= μ x N x I/leff=

L x I/(N x Aac)

)(1

air

airairA

mc

m

ceff AIN

cIN

NIL AB

m

ceff AN

2

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Bmax= Constant @ given material

PC95:Bmax~350mTPC44:Bmax~300mTPC40:Bmax~270mT

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NImax= Constant @ lair, air gap is fixed

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Sundest, MPP, Ferrite…?

Experiment 1st:

Selecting the best Magnetic Material

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Selecting Magnetic Materials

Taiwan AC Adaptor Measurement with different Inductor Materials

83.85%1.2117mH

83.67%0.888mH

83.72%1.31mH

85.91%0.62mH 85.55%

1.2182mH85.53%

1.8382mH84.55%3.08mH

85.89%1.08mH85.35%

0.637mH

85.60%0.533mH84.97%

1.274mH

86.01%1.112mH85.58%

0.988mH85.32%

0.861mH84.62%0.4645mH

85.12%0.4645mH

85.88%0.4645mH

84.86%0.625mH

85.62%0.4295mH

86.97%0.427mH

85.81%0.333mH

85.92%0.288mH

82.00

83.00

84.00

85.00

86.00

87.00

88.00

TF (S

unde

st, O

rigin

al)

TF (8

1 tur

ns w

/ AW

G22

gua

ge w

ire)

TF (1

04 tu

rns

w/ AW

G24 g

uage

wire

)M

PPM

PP

MPP

(0.6

2mH+1

.218

2mH)

Ferri

te (F

rom

ML6

800

Boar

d)

PC95

PC95

PC95 (1

.08m

H//1.0

8mH

)

PC95 (0

.637m

H+0.6

37mH)

PC95, 3

0mils

PC95, 3

0mils

PC95, 3

0mils

PC95, 3

0mils

PC95, 3

0mils

, rea

ch IL

IMIT

PC95, 3

0mils

PC95, R

M8,

36m

ils

PC95, R

M8,

44m

ils

PC95, R

M6,

20m

ils, M

ax P

ower

PC95, R

M6,

30m

ils, M

ax P

ower

PC95, R

M8,

30m

ils

Inductor Materials

Eff

icie

nc

y (

%)

Eff. (%)

Ferrite and MPP have the higher efficiency performance.Ferrite is our selection.

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Ferrite is our selection for Po=100W

Ferrite is Cost Effectiveand

Ferrite Core Loss (AC Loss) is much less

DCR seems dominates the efficiency with Ferrite Core!Let us prove it here!

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290uH or 1mH?

Experiment 2nd:

DCR and switching frequency is fixedWinding Factor is not optimal.

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Eff. (%) vs L (mH)Constant Indcutor Resistance (DCR=0.46 ohm), fSW=67.5kHz

PC95, RM8, lg=30mils

86.01%

85.58%85.32%

84.62%84.50

85.00

85.50

86.00

86.50

0 0.2 0.4 0.6 0.8 1 1.2

L (mH)

Eff

icie

ncy

(%

)

Eff. (%)

With fixed DCR=0.46 ohm and fixed fsw=67.5Khz, Po=100 W and Vo=19V AC Adapter

Higher Efficiency with Higher Inductor?but

it is miss-leading!

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We have learned:

Without the Space Limit,Higher inductance will have the higher efficiency.

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Should we go higher frequency to solve the space issue?

Experiment 3th:

With RM8 and RM6, we fixed crest factor, r=0.95and

Winding Factor is Optimal with the giving bubbin.

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Po=100W, PFC boost OnlyConstant r=crest factor=Ip-p/Irms=0.95

with Constant r=0.95

Higher Efficiency with Higher Inductance?Higher Efficiency with Lower Frequency?

Again, it is miss-leading! From above data, to improve efficiency, we only know that

we should reduce frequency to trade efficiency.

Efficiency (%) vs Freq (kHz)PC40, Crest Factor = 0.95

Efficiency Difference of RM6 = 0.74%Efficiency Difference of RM8 = 1.09%

93.39%

92.76%

92.65%

93.84%93.70%

93.04%92.75%

92.5

93

93.5

94

0 50 100 150 200 250

Freq (kHz)

Eff

icie

ncy

(%

)

RM6

RM8

L (mH) vs Freq (kHz)PC40, Crest Factor = 0.95

0.438

0.303

0.14

0.432

0.3017

0.198

0.141

0

0.1

0.2

0.3

0.4

0.5

0 50 100 150 200 250

Freq (kHz)

L (

mH

)

RM6

RM8

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We have learned:

With the given space, frequency should be as low as possible before the core is saturated.

The Lower Frequency provides the Higher Efficiency

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What will happen with fixed switching frequency?

Experiment 4th:

Optimal Winding Factor for RM8 and fsw = 67.5Khz

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fsw=67.5Khz with CM6800 100W demo board

Efficiency (%) vs L (mH)6800 Board

PC40, RM8, Constant fSW = 67.5kHz

93.75

93.21

92.14

92.75

93.14

92.7292.54

93.37

92.9

9292.2

92.492.6

92.893

93.2

93.493.6

93.894

0 0.5 1 1.5

L (m H)

Eff

icie

nc

y (

%) Pin ~ 110W

Adj Pin Compared toMeasurement on ACAdaptor Board

L=442uH is the Highest Efficiency one; Crest Factor, r~1

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fsw=100Khz with CM6800 100W demo board

L=295uH is the Highest Efficiency one; Crest Factor, r~1

Efficiency (%) vs L (mH)6800 Board

PC40, RM8, Constant fSW = 100kHz

93.75

93.15

93.63

93.75

93.1

93.2

93.3

93.4

93.5

93.6

93.7

93.8

0 0.5 1 1.5

L (mH)

Eff

icie

ncy

(%

)

Pin ~ 109W

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fsw=100Khz with CM6800 100W demo board

L=295uH is the Highest Efficiency one; Crest Factor, r~1

Efficiency (%) vs DCR (ohm)6800 Board

PC40, RM8, Constant fSW = 100kHz

93.15

93.75 93.75

93.63

93.1

93.2

93.3

93.4

93.5

93.6

93.7

93.8

0 0.2 0.4 0.6 0.8

DCR (ohm)

Eff

icie

ncy

(%

)

Pin ~ 109WEfficiency (%) vs L Gap (mils)6800 Board

PC40, RM8, Constant fSW = 100kHz

93.63

93.15

93.75 93.75

93.1

93.2

93.3

93.4

93.5

93.6

93.7

93.8

0 10 20 30 40 50

L Gap (mils)

Eff

icie

ncy

(%

)

Pin ~ 109W Efficiency (%) vs N (turns)6800 Board

PC40, RM8, Constant fSW = 100kHz

93.63

93.7593.75

93.1593.1

93.2

93.3

93.4

93.5

93.6

93.7

93.8

0 20 40 60 80 100

N (turns)

Eff

icie

ncy

(%

)Series1

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fsw=67.5Khz with CM6805 100W AC Adapter

L=295uH is the Highest Efficiency one; Crest Factor, r~1.55

Efficiency (%) vs L (mH)AC Adaptor Board

PC40, RM8, Constant fSW = 67.5kHz

86.04

86.23

85.6185.57

84.88

86.0186.24

85.96

85.43

84.94

84.80

85.00

85.2085.40

85.60

85.80

86.0086.20

86.40

0 0.5 1 1.5

L (mH)

Eff

icie

ncy

(%

) Pin ~ 120W

Adj Pin Compared toMeasurement on6800 Board

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We have learned:

Crest Factor, r~1 to 1.55L=442uH to 295uH for 67.5Khz and L=295uH for

100Khz gives the best efficiency;

It means without saturating the coreReducing DCR, Reducing lg , Reducing N, all will

improve the efficiency.

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Conclusion:

Ferrite: PC95 RM8 (67.5Khz) --- > RM6 (100Khz)

295uHwith CM6805 (PFC+PWM combo IC)

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442uH with fsw = 67.5Khz Vout = 220V, Po = 100W, RM8 and PC 95

• lg = 24 mil• N = 52.5 turns• Pin max = 146.56W• L = 400.58uH x 1.09• Al = 0.1584uH/turn^2

• Ipeak at Sat = 2.3A• DCR = 0.09 ohm

• P core loss ~ 0.39W at Pin max

• P copper loss ~ 0.228W at Pin max

• Total P loss ~ 0.62W at Pin max

• Wire Area = 0.44 mm^2 => AWG=21

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295uH with fsw = 67.5Khz, Vout = 220V, Po = 100W, RM8 and PC 95

• lg = 20 mil• N = 40.5 turns• Pin max = 138.6W• L = 285uH• Al = 0.1738uH/turn^2

• Ipeak at Sat = 2.178A• DCR = 0.05 ohm

• P core loss ~ 0.39W at Pin max

• P copper loss ~ 0.12W at Pin max

• Total P loss ~ 0.51W at Pin max

• Wire Area = 0.57 mm^2 =>AWG=20

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295uH with fsw > 100Khz, Vout = 220V, Po = 100W, RM6 and PC 95

• lg = 32 mil• N = 64.5 turns• Pin max = 118.93W• L = 229uH x 1.23• Al = 0.068uH/turn^2

• Ipeak at Sat = 1.87A• DCR = 0.19 ohm

• P core loss ~ 0.15W at Pin max

• P copper loss ~ 0.33W at Pin max

• Total P loss ~ 0.48W at Pin max

• Wire Area = 0.18 mm^2 =>AWG=25

Jeffrey HwangWinning by Power100W AC Adapter without SR

Efficiency vs. LoadWith 295uH(RM8), 442uH(RM8) and 303uH(RM6)

at fsw = 67.5KhzAC Adaptor Board

Efficiency (%) vs PO (W)

PC95, VIN=90VRMS, RVCC-IAC=25kohm

RM8, L=295uH, DCR=0.1ohm, lg=20mils, N=40RM8, L=442uH, DCR=0.15ohm, lg=20mils, N=50RM6, L=303uH, DCR=0.33ohm, lg=30mils, N=64

79

80

81

82

83

84

85

86

87

88

0 20 40 60 80 100

PO (W)

Eff

icie

nc

y (

%)

RM8, L=295uH, DCR=0.1ohm, lg=20mils, N=40

RM8, L=442uH, DCR=0.15ohm, lg=20mils, N=50

RM6, L=303uH, DCR=0.33ohm, lg=30mils, N=64

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AC Adaptor BoardEfficiency (%) vs Line Voltage (VRMS)

PC95, RVCC-IAC=25kohm

RM8, L=295uH, DCR=0.1ohm, lg=20mils, N=40RM8, L=442uH, DCR=0.15ohm, lg=20mils, N=50

RM6, L=303uH, DCR=0.33ohm, lg=30mils, N=64

85.586

86.5

8787.5

8888.5

8989.5

89 139 189 239

VIN (VRMS)

Eff

icie

ncy

(%

)

RM8, L=295uH, DCR=0.1ohm, lg=20mils, N=40

RM8, L=442uH, DCR=0.15ohm, lg=20mils, N=50

RM6, L=303uH, DCR=0.33ohm, lg=30mils, N=64

100W AC Adapter without SREfficiency vs. Vin

With 295uH(RM8), 442uH(RM8) and 303uH(RM6)at fsw = 67.5Khz

Po=100WPo=66W

Jeffrey HwangWinning by Power100W AC Adapter with SR and without SR

Efficiency vs. VinWith 442uH(RM8)at fsw = 67.5Khz

100W AC AdapterEfficiency with and without SR

84

86

88

90

92

80 130 180 230

Vin (Vrms)

Effi

cien

cy (%

)

without SR

with SR

Measure the Efficiency Data at the end of cables.