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

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A Low Output Ripple DC to DC converter topology
using voltage overlapping technique
The Power Electronics Lab., Hong Kong
University C. P. Liu N. K. Poon M. H. Pong
Speaker C.P.Liu
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Low output ripple solutions Interleaving
Input voltage 36V Duty cycle 0.5 Ripple
current p-p 0A !!
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Low output ripple solutions Interleaving
Input voltage 72V Duty cycle 0.25 Ripple
current p-p 20.833A ??
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Low output ripple solutions Interleaving
Ripple current vs. Input voltage
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Low output ripple solutions Single phase
Ipp
f2x
L 266nH
Interleave converter
Even better than Multi-phase
Single phase converter
Question Why 266nH and freq 2 x f ?
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One inductor reduces resistance
2
1
1
1
Ae
Ae
2(1111)8
(1212)6
For same copper loss
N 4/3
N 1
For same flux density
L (16/9 x 300/2) nH
L 300nH
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Ultimate interleaving 5050
? ?1?2
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What if more than 50 ?
Vp
Vp
Vp
Pure DC from AC pulse
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No regulation - stupid!
Vp
Vp
Vp
Need Amplitude Modulation
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Simplest Amplitude Modulator
Vp
Vp(1-D)
Vp
Vp(1-D)
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Worlds first wide range wide loading output
capacitorless DCDC regulator.
Va
Vb
Stupid again!
Vo
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Worlds first wide stupid DCDC regulator.
More components than a already good interleaving
converter ! !
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Isolated Overlap VS Isolated Interleave
Compare with the more complicated approach
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No perfect DC blocking capacitor
Va
Va
Vb
Vb
Vo
Ripple voltage introduced
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Of course an O/P capacitor is needed
Vo
ICo
Resonate current pulse
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Final configuration add a current source
Ls ltlt Lo
Va
Lo
Ls1
Vb
ILs1
Ls2
ILs2
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Overlapping Sync-Rect
Circulating current, becareful.
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Overlapping Active Diode
36V-72V
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Overlapping or Interleaving
2A p-p
20.8A p-p
Same O/P Inductor Same 72V I/P voltage Same D0.5
at 36V I/P
300 nH
300 nH
300 nH
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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