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Series Resonant Converter with Series-Parallel Transformers for High Input Voltage Applications

C-H Chien1,B-R Lin2,and Y-H Wang1

1 Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, Tainan 701, Taiwan

2 Department of Electrical Engineering, National Yunlin University of Science and Technology, Yunlin 640, Taiwan

2

Outline

Introduction Circuit configuration Experimental results Conclusion

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Introduction

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For 3-phase 380V (or 480V) AC/DC converters the DC bus voltage > 500V (or 650V)

∴ select suitable power MOSFETs → difficult 3 level neutral-point clamp converter → overcome these drawbacks

more power switches more circuit components high cost complicated control schemes split capacitors and clamp diodes

the Vstress of MOSFETs → ½ DC bus voltage

What’s for in this study?

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What’s new in this study? A novel DC/DC converter (24V/40A, 960W)

2 circuit modules for high voltage application 2 capacitors and 2 half-bridge

series in high Voltage clamp the Vstress of MOSFET

Vstress = ½ input V

interleaved switching signal→ phase-shift ¼ switching T → 90° reduce ripple current (input and output) share the load current reduce the size of magnetic core

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Why is the topology ?

A series resonant tank high conversion efficiency high power density 2 series Transformers

balance the 2 winding current all semiconductors soft switching

switching loss ↓ ∵ (ZVS & ZCS)

wide input voltage and load 480V~600V all load

2 windings in parallel Istress ↓

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Circuit configuration

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Circuit configuration and key waveforms

Key waveforms Circuit configuration

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Different modes during 1 period

Mode 1

Mode 2

Mode 3

Mode 4

Mode 5

Mode 6

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Mode 1 ( t0≦t ＜ t1 ) S1 off , S2 → off

VLm1=nVo= VLm2

Cs1, Cs2, and Lr1 → resonant iLr1

Cs2 => from 0 V → Vin/2 → charge Cs1 => from Vin/2 → 0 V → discharge

iLm1 → iLm2 → iD1 → iD3 →

mmmm

LmLm LLLL

ttnVtiti

21

00022 ,

)()()(

))()(()( 111 titinti LmLrD

))()(()( 213 titinti LmLrD

s

p

m

LmLmn

nn

L

ttnVtiti

,

)()()( 00

011

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Mode 2 ( t1≦t ＜ t2 ) S2 off , S1 → ZVS→ on

iLm1= iLm2= iLr1 → mode end VLm1=nVo= VLm2

Cr1 and Lr1 → resonant applied voltage = (Vin/2 － 2nV0)

iLm1 ,iLm2 linearly ↑ slope = nV0/Lm

iLr1 → Vcr1→

)(cos)()(sin)(22/

)( 111111

1 tttittZ

tvnVVti rLrr

r

croinLr

)(sin)()(cos)](2/[22/)( 1111111 ttZtitttVnVVnVVtV rrLrrcroinoinCr

1

1

11

, 1

r

rr

rr

r C

LZ

CL

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Mode 3 ( t2≦t ＜ t3 ) S2 off , S1 → on → off

iLm1= iLm2= iLr1 → mode start S1 off → mode end iD1=iD2=iD3=iD4=0 Cr1, Lr1, Lm1, and Lm2 → resonant iLr1 →

Vcr1 →

)(cos)()(sin)(2/

)( 221221

1 tttittZ

tvVti pLrp

p

crinLr

)(sin)()(cos)](2

[2

)( 2212211 ttZtitttVVV

tV ppLrpcrinin

Cr

1

211

1211

)( ,

)(

1

r

mmrr

rmmr

p C

LLLZ

CLLL

13

Mode 4 ( t3≦t ＜ t4 ) S2 off , S1 → off

VLm1=-nVo= VLm2 Cs1, Cs2, and Lr1 → resonant iLr1

Cs1 => from 0 V → Vin/2 → charge Cs2 => from Vin/2 → 0 V → discharge

iLm1 ,iLm2 linearly ↓ slope = -nV0/Lm

Vcs1 → Vcs2 → iD2 →

iD4 →

))()(()( 112 titinti LrLmD

))()(()( 214 titinti LrLmD

2133

1 ),(2

)()( 1

ssss

Lcs CCCtt

C

titV r

)(2

)(

2)( 3

32

1 ttC

tiVtV

s

Lincs

r

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Mode 5 ( t4≦t ＜ t5 ) S1 off , S2 → ZVS → on

iLm1= iLm2= iLr1 → mode end VLm1=-nVo= VLm2

Cr1 and Lr1 → resonant applied voltage = 2nV0

iLm1 ,iLm2 linearly ↓ slope = -nV0/Lm

iLr1 → Vcr1→

)(cos)()(sin)(2

)( 441441

1 tttittZ

tvnVti rLrr

r

croLr

)(sin)()(cos)](2[2)( 4414411 ttZtitttVnVnVtV rrLrrcrooCr

1

1

11

, 1

r

rr

rr

r C

LZ

CL

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Mode 6 ( t5≦t ＜ t0 ) S1 off , S2 → on → off

iLm1= iLm2= iLr1 → mode start S2 off → mode end iD1=iD2=iD3=iD4=0 Cr1, Lr1, Lm1, and Lm2 → resonant iLr1 →

Vcr1 →

)(cos)()(sin)(

)( 551551

1 tttittZ

tvti pLrp

p

crLr

)(sin)()(cos)()( 5515511 ttZtitttVtV ppLrpcrCr

1

211

1211

)( ,

)(

1

r

mmrr

rmmr

p C

LLLZ

CLLL

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Key circuit parameters of the prototype circuit

Input voltage Vin → 480V ~ 600V Input nominal Vin,norm → 530V Output voltage Vo and current Io → 24V / 40A Series resonant frequency fr → 100kHz Switches S1~S4 → IRFP460 Diodes D1~D8 → MBR3060PT Turns ratio of T1~T4 → np:ns1:ns2=20:6:6 Resonant inductances Lr1~ Lr2 → 21 μH Magnetizing inductances Lm1~ Lm4 → 82 μH Resonant capacitances Cin1~ Cin2 → 330 μF/400V Output capacitances Co → 2200 μF/50V

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Experimental results

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The interleaved signals of switches

Experimental waveforms of gate voltages

S1~S4 at full load Vin=530V

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The ZVS of switches under input 530V

Experimental gate V, drain V and drain I of switch S1

Vin → 530V load → 25%

Experimental gate V, drain V and drain I of switch S1

Vin → 530V load → 100%

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The ZCS of rectifier diodes under input 530V

Measured waveforms of gate voltages vS1,gs and vS3,gs

Output currents of each center tapped rectifier at full load nominal input voltage

Vin=530V turn off

ZCS

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Switching Frequency VS. Output Power

Measured switching frequencies at different input

voltages at different load

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Conclusion

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A resonant converter with the series half-bridge legs for high DC bus voltage application

Two circuit modules share the load power

For each module series-connected in primary side parallel-connected in secondary side power MOSFETs → turn on ZVS rectifier diodes → turn off ZCS

Conclusion

switching loss↓

balance 2 winding current

share the load current

The voltage stress of each switch=0.5Vin

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Thanks for your attention!