Soft-Switching DC-DC Converter

Is to shape the voltage or the current waveform by creating a resonant condition to:

Force the voltage across the switching device to drop to zero before turning it ON Zero-Voltage Switching (ZVS)

Force the current through the switching device to drop to zero before turning it OFF Zero-Current Switching (ZCS)

Overview

• Many soft-switching dc-dc converter families were introduced in the open literature

• The objectives of these topologies are to develop high switching frequency converters with high power density and high efficiency

• This was accomplished by adding additional components to the power stage.

• Steady-state analysis tend to be time consuming.

• Provided little insight into the converter switching-cell operation.

Hard-Switching and Soft-Switching

Hard-Switching

Zero-Current SwitchingZero-Voltage Switching

Why Soft-Switching?

• Reduce switching losses especially at high switching frequencies

• Increase the power density, since the size and weight of the magnetic components is decreased by increasing the operating frequency

• Reduce the Electromagnetic Interference (EMI)

Conventional DC-DC Converters(Hard-Switching)

V in

+

-

V g

S

+

-vD

IF

iD

iswa

b

c

D C o

L o

R o

+

-

V o

IoI in +

-

V g

IF

a

+

vD

iD

c

S

isw

V F

-

bD

V inC o R o

+

-

V o

L o

+ -

V g

SIF

iswa c +-vD

iD b

D

V in C o R oL o

+

-

V o

I in

a

c

V in S

isw

D S

R o

+

-

V o

+

vD

iD

-

b

D C o

L oL i

+ -V g

C i

V in

S

iswa c

C o

L o

R o

+

-

V o

+

-vD

iD

b

DL i

C i

a

c

V in S

isw

b

L o

L i C i

R o

-

+

V oC o

+ vDiD -

D

Buck Boost

Buck-Boost Cuk

Zeta Sepic

Switching-Cell Sharing

All the Conventional DC-DC Converters shares the same

switching-cell

With different orientation of the cell in a specific converter

+

-

V g

+

-vD

IF

iD

a

b

c

D

S

isw

The Conventional DC-DC Switching-Cell

Switching-CellVg=Vab Vbc

-

+

+

-

IF

b

a c

Analyzed Soft-Switching Cells

(a)

(b) (c) (d)

(e) (f) (g)

+

-

V g

+

-vD

IF

iD

a

b

c

D

S

isw

+

-

V g

+

-vD

IFiLr

iD

a

b

c

L r

D

S

+ -vcr

D S

C r

vD

+

+

-

V g

IFiLr

iD

a

b

c

L rS

+

-vcr C r

-D

+

-

V g

S

+ -

+

+

-

-

V F

vcr

vD

IF

iLr

iD

a

b

c

C FL r

D S

D

C r

+

-

V g

IFiLra

b

c

SvD

+

-D

+

-

vcr C r LT

iT

D 1 L r +

-

V g

S

+

+

-

-

vcr

vD

IF

iDisw

a

b

c

L r

D S

D

C r

S 1

D 1

isw1

+

-vD1

+

-

V g

S

+

-vD

IF

iDisw

a

b

c

L r

D S1D

C r

S 1

D 1

isw1

+

-vD1

(a) Conventional Cell, (b) ZVS-QRC Cell, (c) ZCS-QRC Cell, (d) ZVS-QSW CV Cell, (e) ZCS-QSW CC Cell,(f) ZVT-PWM Cell, and (g) ZCT-PWM Cell

Zero-Voltage-Switching Quasi-Resonant

+

-

V g

+

-vD

IFiLr

iD

a

b

c

L r

D

S

+ -v cr

D S

C r

t2 t3t0 t0+T s

t

DS

iLr

V g

IF

t1

vCrV g+Z oIF

-IF

tc,on

ZVS-QRC Switching-Cell ZVS-QRC Cell Basic Switching-Waveforms

ZVS-QRC Family

+

-

V g

S

+

+

-

-

v cr

vD

IF

iD

a

b

cD S

D

C r

V in

L o

C o R o V o

IoI in

+

-

iL r

L r

+

-

V g

S

+

+

-

-

v cr

IFiLr

iD

a

bc

L r

D S

D

C r

R o

Io

V oC o

+

-

I inL i

V in

vD

+ -

V g

S

+

+

-

-

v cr

vD

iL r

a bcD S

D

C r

IF

iD

C o R o V o

Io

+

-

LV in

I in

L r

L r

S

+

+-

-

v cr

vD

iL r

iD

a b

c

L r

D S

D

C r

R o V oC o

+

-

I in L i

V in

L o IoV g

+ -

C i

S

+

+

-

-

v cr

vD

IF

iLr

iD

a

b

cL rD S

D

C r

V in

L o

C o R o V o

IoI in

+

-L i

C i

S

+

+

-

-

v cr

vDiLr iD

a

bc

L r

D S

D

C r

R o

Io

V oC o

+

-

I inL i

V in L o

C i

ZVS-QRC Buck ZVS-QRC Boost

ZVS-QRC Buck-Boost ZVS-QRC Cuk

ZVS-QRC Zeta ZVS-QRC Sepic

Zero-Current-Switching Quasi-Resonant

vD

+

+

-

V g

IFiLr

iD

a

b

c

L rS

+

-v cr C r

-D

t2 t3t0 t0+T s

t

DS

iLr

IF

t1

vCr

IF+V g/Z o

2V g

tCr-ptLr-p

ZCS-QRC Switching-Cell ZCS-QRC Cell Basic Switching-Waveforms

ZCS-QRC Family

+

-

V g

S

+

+-

-v cr vD

IF

iD

isw

a

b

c

DC rV in

L o

C o R o V o

IoI in

+

-

iLr

L r

+

-

V g

S

+

+

-

-

v cr

IFiLr

iD

isw

a

bc

L r

D

C r

R o

Io

V oC o

+

-

I inL i

V in

vD

+ -

V g

S

+

+

-

-

v cr

vD

iLrisw

a bc

DC r

IF

iD

C o R o V o

Io

+

-

LV in

I in

L r

L r

S

+

+ -

-v crvD

iL r

iD

isw

a b

c

L r

DC r R o V oC o

+

-

I in L i

V in

L o IoV g

+ -

C i

S

+

+ -

-v crvD

IF

iLr

iD

isw

a

b

cL r

DC rV in

L o

C o R o V o

IoI in

+

-L i

C i

S

+

+

-

-

v cr

vDIFiLr

iD

isw

a

bc

L r

D

C r

R o

Io

V oC o

+

-

I inL i

V in L o

C i

ZCS-QRC Buck ZCS-QRC Boost

ZCS-QRC Buck-Boost ZCS-QRC Cuk

ZCS-QRC Zeta ZCS-QRC Sepic

ero-Current-Transition PWM Cell

+

-

V g

S

+

-vD

IF

iDisw

a

b

c

L r

D S 1D

C r

S 1

D 1

isw 1

+

-vD 1

tx t2 t3 t4t0 t0+T s

t

1-D

D 1

S

S1

Vcr

iLr

iswIF

IF

V Crp

-V Crp

t1

ILrp

ZCT-PWM Switching-Cell

ZCT-PWM Cell Basic Switching-Waveforms