New Common Mode Filter Combining Differental Filter

1
Technique for LLC Series Resonant DC/DC Converter
2
Contents 1. Problems of Conventional DC/DC
Converter 2. Principle of Proposed LLC-SRC 3.
Experimental Verification 4. Application
Examples 5. Conclusions
3
Problems of Conventional PWM Converter
Forward
Asymmetrical H/B
Phase Shift F/B

• Efficiency declines when high input

• Reverse recovery problem for rectifier

4
Problems of Conventional Resonant Converter
Series resonant
Parallel resonant
LCC series parallel resonant

• Large frequency variation
• Failure at no load

• Small frequency variation
• High circulation energy

• Lower circulation energy
• Efficiency optimized at low input

5
Principle of LLC-SRC
Vin
Vo
S1
Cs
Tr
D1
C2
C1
Lm
Ls
D2
S2
Proposed Half-bridge LLC Series Resonant
Converter (LLC-SRC)
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Comparison with Conventional SRC
Ls
Cs
Ls
Cs
OUT
OUT
IN
IN
Lm
Load
Load
Conventional SRC
LLC-SRC
GainOUT/IN

• ZVS operation range
• Conventional SRC fgtfs
• LLC-SRC fgtfm

LLC-SRC (Lm37Ls)
1
Conventional SRC

• fmltfltfs ZCS for rectifiers

frequency
fm
fs
7
Operation Waveforms
fmltfltfs
iC1
Cs
S1
S1
S2
iLs
C1
Lm
im
Im
im
Ls
S2
iLs
Tr
iLd
D1
C2
vAB
iLd
D2
8
Operation Waveforms
fmltfltfs
iC1
Cs
S1
S1
S2
iLs
C1
Lm
im
Im
im
Ls
S2
iLs
Tr
iLd
D1
C2
vAB
iLd
D2
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Operation Waveforms
ffs
iC1
Cs
S1
S1
S2
C1
Lm
iLs
Ls
im
S2
Tr
iLs
iLd
D1
vAB
C2
iLd
D2
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Operation Waveforms
fgtfs
iC1
Cs
S1
S1
S2
iLs
C1
Lm
im
Ls
S2
Tr
iLs
iLd
D1
vAB
C2
iLd
D2
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Regulation Equation of LLC-SRC
Ls
Cs
nVo
fltfs
fgtfs
ffs
nVo
nVo
nVo
Vin/2
Vin/2
Vin/2
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Experimental Verification
SPECIFICATIONS INPUT 40 V - 60 V
OUTPUT 24 V / 10 A Frequency 75kHz Higher
PARAMETER SELECTION
S1 , S2 IRF3710 D1 D2 40CPQ60 Core
EE32/16/9 n 6 6 Cs 1.6uF Ls
1uH (leakage inductance) Lm 6uH
Test Circuit
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Measured operation waveforms
Driver signal of switch
Vds of the switch
Resonant Current
Voltage of output diode
Vin40V f94kHz lt fs (125kHz)
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Measured operation waveforms
Resonant Current is close to sine wave.
Vin50V f112kHz fs
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Measured operation waveforms
Voltage overshot. ZCS condition was lost.
Vin60V f133kHz gt fs
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Efficiency of test circuit Vin4060V, Vo24V
_at_24V/10A Output
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Application for holdup time requirement
1kW, 400V input and 54V/20A output sever
power S1,S2 IRFP37N50A D1,D2 30CPQ150
Tr EE42/20 3C85
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Parameters of Two Designs
Input Range Ls Cs Lm n
A 300400V 20uH 88uF 120uH 205
B 200400V 20uH 108uH 50uH 175
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Tested Efficiency (1kW, 54V/20A)
A 300V400V input design B 200V400V input
design
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Frequency Variation Rang
_at_54V output
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Primary switches
Output Capacitors
Output Rectifier
Transformer
1kW, 400V input and 54V/20A output
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Application for high power and high input
voltage
Full-Bridge Structure
High input voltage
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Conclusions

• Features of LLC-SRC
• Simple and flexible structure
• ZVS for switches and ZCS for rectifiers
• Conversion efficiency optimized at high input
• Applications
• High input voltage
• Higher output voltage
• Holdup time requirement