Jeffrey Hwang Winning by Power Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang Design a 100W...

Jeffrey HwangWinning by Power

Alland Chee, Elvis Lin, Joe Wong

and

Jeffrey H. Hwang

Design a 100WPFC Boost Inductor


Criteria of Selection

Size

Efficiency

Cost


• 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


• 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


Bmax= Constant @ given material

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


NImax= Constant @ lair, air gap is fixed


Sundest, MPP, Ferrite…?

Experiment 1st:

Selecting the best Magnetic Material


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.


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!


290uH or 1mH?

Experiment 2nd:

DCR and switching frequency is fixedWinding Factor is not optimal.


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!


We have learned:

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


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.


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


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


What will happen with fixed switching frequency?

Experiment 4th:

Optimal Winding Factor for RM8 and fsw = 67.5Khz


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


fsw=100Khz with CM6800 100W demo board


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


fsw=100Khz with CM6800 100W demo board


Efficiency (%) vs DCR (ohm)6800 Board


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


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


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


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


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.


Conclusion:

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

295uHwith CM6805 (PFC+PWM combo IC)


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


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





• Wire Area = 0.57 mm^2 =>AWG=20


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





• 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




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


85.586

86.5

8787.5

8888.5

8989.5

89 139 189 239

VIN (VRMS)

Eff

icie

ncy

(%

)




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.

Jeffrey Hwang Winning by Power Alland Chee, Elvis Lin, Joe Wong and Jeffrey H. Hwang Design a 100W...

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