Transcript A Low Output Ripple DC to DC converter topology using

PowereLab HKU
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
Prepared by Franki Poon
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Low output ripple solutions – Interleaving
f1x
Input voltage = 36V
Duty cycle = 0.5
Ripple current p-p = 0A !!
L=300nH Ipp
17.917
20
15
I1( t  36)
10
I2( t  36)
I1( t  36)  I2( t  36)
f1x
5
0
L=300nH
 2.917
5
0
0
Prepared by Franki Poon
5 10
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1 10
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1.5 10
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2 10
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2.5 10
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3 10
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3.5 10
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4 10
t
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4.5 10
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5 10
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6.5 10
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6
7.510
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Low output ripple solutions – Interleaving
f1x
Input voltage = 72V
Duty cycle = 0.25
Ripple current p-p = 20.833A ??
L=300nH Ipp
25.417
30
20
I1( t  72)
I2( t  72)
10
I1( t  72)  I2( t  72)
f1x
0
L=300nH
 8.125 10
0
0
Prepared by Franki Poon
5 10
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1 10
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1.5 10
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2 10
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2.5 10
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3 10
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3.5 10
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4 10
t
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4.5 10
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5 10
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5.5 10
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6.5 10
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6
7.510
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Low output ripple solutions – Interleaving
f1x
L
Ipp
Ripple current vs. Input voltage
30
20
 
Iripple Vi
10
L
f1x
0
35
40
45
50
55
60
Vi
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65
70
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Low output ripple solutions – Single phase
20.833
 
20
I ripple V i
Ipp
f2x
30
 
I ripple_single_phase V i
10
L = 266nH
0
0
35
36
40
45
50
55
60
65
70
75
Vi
72
Interleave converter
Even better than
Multi-phase
Prepared by Franki Poon
Single phase converter
Question: Why 266nH and freq = 2 x f
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?
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One inductor reduces resistance
2
1
1
Ae
Ae
2(1+1+1+1)=8
1
Ae
Ae
(1+2+1+2)=6
For same copper loss:
N=1
N = 4/3
For same flux density:
L = 300nH
Prepared by Franki Poon
L = (16/9 x 300/2) nH
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Ultimate interleaving – 50%+50%
 = 12
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What if more than 50% ?
Vp
Vp
Vp
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No regulation - stupid!
Vp
Vp
Vp
Vp
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Vp
Vp
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Simplest Amplitude Modulator
D
Vp
Vp(1-D)
D
Vp
Vp(1-D)
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World’s first wide range & wide loading
output capacitorless DCDC regulator.
Va
Va
Vo
Vb
Vb
Vo
Prepared by Franki Poon
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World’s 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
Va
Vo
Vb
ICo
Resonate
current pulse
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Final configuration – add a current source
Ls << Lo
Ls1
Va
Lo
Vb
ILs1
Ls2
ILs2
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Overlapping + Sync-Rect
Va
Ls1
Vb
Ls2
ILs1
ILs2
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Overlapping + Active Diode
O/P Inductor
current
36V-72V
O/P diodes
current
0.33 uF
50 nH
300 nH
Gate drive
Gate drive
100 uF
0.33 uF
50 nH
2.5V@15A
Efficiency = 88%
O/P ripple = 50mV
fs = 200kHz
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Overlapping or Interleaving
2A p-p
300 nH
20.8A p-p
Same O/P
Inductor
300 nH
Same 72V I/P
voltage
300 nH
Same D=0.5
at 36V I/P
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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


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14V, 36A with tight
regulation
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Thank you
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