A Low Output Ripple DC to DC converter A Low Output Ripple DC to DC converter topology using voltage overlapping topology using voltage overlapping techniquetechnique

The Power Electronics Lab., Hong Kong The Power Electronics Lab., Hong Kong UniversityUniversity

C. P. LiuC. P. Liu N. K. Poon N. K. Poon M. H. PongM. H. Pong

Speaker Speaker

C.P.LiuC.P.Liu

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Low output ripple solutions – InterleavingLow output ripple solutions – Interleaving

Input voltage = 36VDuty cycle = 0.5Ripple current p-p = 0A !!

0 5 10 7 1 10 6 1.5 10 6 2 10 6 2.5 10 6 3 10 6 3.5 10 6 4 10 6 4.5 10 6 5 10 6 5.5 10 6 6 10 6 6.5 10 6 7 10 6 7.5 10 65

0

5

10

15

2017.917

2.917

I1 t 36( )

I2 t 36( )

I1 t 36( ) I2 t 36( )

7.5 1060 t

f1x

f1x

IppL=300nH

L=300nH

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Low output ripple solutions – Low output ripple solutions – InterleavingInterleaving

Input voltage = 72VDuty cycle = 0.25Ripple current p-p = 20.833A ??

0 5 10 7 1 10 61.5 10 6 2 10 6

2.5 10 6 3 10 63.5 10 6 4 10 6 4.5 10 6 5 10 6 5.5 10 6

6 10 6 6.5 10 67 10 6 7.5 10 6

10

0

10

20

3025.417

8.125

I1 t 72( )

I2 t 72( )

I1 t 72( ) I2 t 72( )

7.5 1060 t

f1x

f1x

L=300nH Ipp

L=300nH

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Low output ripple solutions – Low output ripple solutions – InterleavingInterleaving

f1x

f1x

L

L

Ipp Ripple current vs. Input voltage

35 40 45 50 55 60 65 70 750

10

20

30

Iripple Vi

Vi

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Low output ripple solutions – Single phaseLow output ripple solutions – Single phase

f2x

L = 266nH

Ipp

Even better than Multi-phase

35 40 45 50 55 60 65 70 750

10

20

3020.833

0

I ripple V i I ripple_single_phase V i

7236 V i

Question: Why 266nH and freq = 2 x f ?

Interleave converter

Single phase converter

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2(1+1+1+1)=8 (1+2+1+2)=6

One inductor reduces resistanceOne inductor reduces resistance

1

1

Ae Ae 1

2

Ae Ae

For same copper loss:

N = 4/3N = 1

For same flux density:

L = 300nH L = (16/9 x 300/2) nH

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Ultimate interleaving – Ultimate interleaving – 50%+50%50%+50%

= 12

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What if more than 50% ?What if more than 50% ?

Vp

Vp

Vp

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Vp

Vp

Vp

No regulation - stupid!No regulation - stupid!

Vp

Vp

Vp

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Vp(1-D)

VpD

Vp(1-D)

VpD

Simplest Amplitude ModulatorSimplest Amplitude Modulator

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World’s first wide range & wide World’s first wide range & wide loading output capacitorless DCDC loading output capacitorless DCDC regulator.regulator.

Va

Vb

Vo

Vo

Va

Vb

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More components than a already good interleaving converter ! !

World’s first wide stupid DCDC World’s first wide stupid DCDC regulator.regulator.

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Isolated Overlap VS Isolated Isolated Overlap VS Isolated InterleaveInterleave

Compare with the more complicated approach

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Vo

Va

Vb

No perfect DC blocking capacitorNo perfect DC blocking capacitor

Ripple voltage

introduced

Va

Vb

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Vo

ICo

Of course an O/P capacitor is neededOf course an O/P capacitor is needed

Resonate current pulse

Va

Vb

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Final configuration –Final configuration – add a current add a current sourcesource

Ls << LoLoLs1

Ls2

ILs2

Va

Vb

ILs1

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Overlapping + Sync-RectOverlapping + Sync-Rect

ILs2

Va

Vb

ILs1

Ls1

Ls2

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Overlapping + Active DiodeOverlapping + Active Diode

300 nH50 nH

100 uF

50 nH

0.33 uF

0.33 uF

36V-72V

O/P Inductor current

O/P diodes current

Gate drive

Gate drive

2.5V@15A

Efficiency = 88%

O/P ripple = 50mV

fs = 200kHz

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Overlapping or Interleaving Overlapping or Interleaving

300 nH

300 nH

2A p-p 20.8A p-p

300 nHSame O/P Inductor

Same 72V I/P voltage

Same D=0.5 at 36V I/P

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After all . . . After all . . .

•Good reasons to look for more low output ripple configurations

•A simple configuration producing very low output ripple current is proposed

•ZVS of primary switches is possible

•Output ripple is independent on input voltage

•Low stress on MOSFET

•Good for low voltage high current applications

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Potential application Intermediate bus

in 48V system 2.8 x 4.5 inches2

500W output

14V, 36A with tight regulation

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Thank you

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