High Step -up Ratio DC -DC Converter Topologiesantenor/pdffiles/High_Step_Up_Converters... · High Step -up Ratio DC -DC Converter Topologies P. Tenti, L. Rossetto , G. Spiazzi, S.

HighHigh StepStep--up Ratio DCup Ratio DC--DC DC Converter TopologiesConverter Topologies

P. P. TentiTenti, L. , L. RossettoRossetto, G. , G. SpiazziSpiazzi, S. , S. BusoBuso, P. , P. MattavelliMattavelli, , L. L. CorradiniCorradini

Dept. of Information Engineering Dept. of Information Engineering –– DEIDEIUniversity of PadovaUniversity of Padova

Speaker: G. Speaker: G. SpiazziSpiazzi

Part IPart I

2

Seminar OutlineSeminar Outline

• Why we need high step-up ratio converters?– Application fields

• Low power high step-up ratio topologies– Coupled inductors

• High power high step-up ratio topologies– Non isolated

– Isolated

3

High StepHigh Step--up Ratio Topologiesup Ratio Topologies

• Low-voltage high-current energy sources– Fuel-cells (some kW)

– Paralleled photovoltaic modules in domestic applications (some kW)

– Microinverter, i.e. connection of a single photovoltaic module to the grid (some hundred watts)

• Step-down inverters require an input voltage higher than the maximum line voltage peak

Why?Why?

4

Example of Example of MicroinverterMicroinverter

• Modularity• Reduction of partial shading effects• Dedicated Maximum Power Point Tracker (MPPT)

200-300W single pv panel

Utility

grid

High Step-Up

DC-DC

Microinverterfor single panel

MicroinverterMicroinverterstructurestructure

5

Simple Boost TopologySimple Boost Topology

( )( )

( )oo

o

D2

o

LSDR,U,dF

d11

UU

d1R

rdrd1r1

1d1

1M ⋅

−=

+−

++−+−=

Switch model

L

C

D

S

+

Ui Uo

+

-

Io+UDIL

Ro

rD

rS

rL

Diode model

Boost scheme including some parasitic elements:Boost scheme including some parasitic elements:

Voltage Voltage conversion ratio conversion ratio (neglecting inductor

current ripple):

6


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

2

4

6

8

Duty-cycle

M

Ro

ideal

Voltage conversion ratio Voltage conversion ratio MM including including conduction losses:conduction losses:

Mmax

7


Converter Converter efficiency:efficiency:

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.7

0.75

0.8

0.85

0.9

0.95

1ηηηη

Ro

Duty-cycle

( ) ( )ooLi

Do

ii

oo

in

out R,U,dFd1MIUIU

IUIU

PP =−====η

8

Low Power Applications Low Power Applications

Ug

U1

U2

+

+

D2

D1S

1:n21

ig

Ld

Lmim

Uo

+

-C1

C2

•• ExampleExample: integrated Boost-Flyback converter

It can be seen as a flyback converter with a non dissipative snubber: D1 and C1 deliver to the output the energy stored

in the transformer leakage inductance Ld

9

Integrated BoostIntegrated Boost--FlybackFlyback ConverterConverter

Ideal waveforms:Ideal waveforms:-- CCM operation of CCM operation of flybackflyback sectionsection-- DCM operation of boost sectionDCM operation of boost section

ig

im

iD1

iD2

t

t

t

t0 t1 t2 t3 t4=Ts-t0

Ug

U1

U2

+

+

D2

D1S

1:n21

ig

Ld

Lmim

Uo

+

-C1

C2

iD2

iD1

Advantages:Advantages:•• ZCS turn on ZCS turn on •• Soft diode turn offSoft diode turn off•• Reduced switch Reduced switch voltage stressvoltage stress

10

Integrated BoostIntegrated Boost--FlybackFlyback ConverterConverter

Problems:Problems:

Parasitic oscillations at DParasitic oscillations at D22 turn off caused by its turn off caused by its capacitance Ccapacitance Crr resonating with transformer leakage resonating with transformer leakage inductances Linductances Ldd and Land Lss

High voltage stress across D2Ug

U1

U2

+

+

D2

D1S

1:n21

ig

Ld

Lmim

Uo

+

-

Ls

is

C1

C2

ur+

Cr

Dissipative R-C-D snubberis needed

11

Modified IBF ConverterModified IBF Converter

Clamping diode D3 added to the original topology

Advantages:Advantages:•• Clean diode voltage Clean diode voltage waveforms without parasitic waveforms without parasitic oscillationsoscillations

•• Energy transfer toward the Energy transfer toward the output also during switch turn output also during switch turn on intervalon interval

•• Slight voltage gain increase Slight voltage gain increase due to resonances between due to resonances between parasitic componentsparasitic components

Ug

U1

U2

+

+

D2

D1

D3

S

1:n21

ig

Ld

Lmim

Uo

+

-

Ls

is

C1

C2

ur+

Cr

x

12


Interval T01 = t1-t0ig

im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2

+

+

D2

S

ig

Ld

Lmim

Uo

+

-

Ls

C1

C2

iD2

13



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2

+

+S

ig

Ld

Lmim

Uo

+Ls

C1

C2

ur+

Cr

-

14



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Note: actual iD3 slope can be either positive or negativeNote: actual iD3 slope can be either positive or negative

Ug

U1

U2

+

+

D3

S

ig

Ld

Lmim

Uo

+Ls

iD3

C1

C2

-

15



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2

+

+D1

D3

S

ig

Ld

Lmim

Uo

+Ls

iD1

C1

C2

-

iD3

16



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2

+

+D1

ig

Ld

Lmim

Uo

+Ls

C1

C2

-

ur+

Cr

iD1

17



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2

+

+

D2

D1

ig

Ld

Lmim

Uo

+Ls

C1

C2

-

iD1

iD2

18



im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0t2 t5

U1

U2

+

+

D2Lmim

Uo

+Ls

C1

C2

-

iD2

19

Converter ParametersConverter Parameters

• Input voltage: Ug = 25-35 V

• Output voltage: Uo = 400 V

• Nominal output power: Po = 300 W

• Switching frequency: fs = 100 kHz

• Magnetizing inductance: Lm = 20 µH

• Primary leakage inductance: Ld = 0.4 µH

• Secondary leakage inductance: Ls = 2 µH

20

Voltage Conversion RatioVoltage Conversion Ratio

5

9

13

17

21

0.4 0.5 0.6 0.7 0.8

M

4

4.4

4.8

5.2

5.6M1

Duty-cycle

g

o

U

UM =

g

11 U

UM =

Comparison between calculations and spice simulations

This unmatched point corresponds to a

different topological sequence

21

Voltage Conversion RatioVoltage Conversion Ratio

g

o

U

UM =

Effect of resonant intervals on the overall voltage gain

0.4 0.45 0.5 0.55 0.6 0.65 0.76

7

8

9

10

11

12

13

14M

Duty-cycle

No parasitic components

With parasitic components

22

Experimental ResultsExperimental Results

Ug = 35 V, Uo = 400 V, Po = 300 W

ig [2.5A/div]

uDS [50V/div

ux [100V/div]

Peaking due to a small dip in the converter input voltage due to fast current rise time

23


Ug = 35 V, Uo = 400 V, Po = 300 W

ig

im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0

Impk

t2 t5

t0 t1 t2

ig

uDS

ux

t3t4 t5

ig

uDS

ux

t6

24


Ug = 25 V, Uo = 400 V, Po = 300 W

t0 t1 t2 t3

ig [5A/div]

uDS [50V/div

ux [100V/div]

Ug

U1

U2

+

+

D3

S

ig

Ld

Lmim

Uo

+Ls

iD3

C1

C2

-

D3 turns off during the switch on interval

25

Measured EfficiencyMeasured Efficiency

Po = 300 W

0.92

0.93

0.94

0.95

25 27 29 31 33 35Ug [V]

ηfs = 100kHz

fs = 200kHz

0.90

0.91

0.92

0.93

0.94

25 27 29 31 33 35Ug [V]

η

fs = 200kHz

fs = 100kHz

Po = 200 W

26


0.92

0.93

0.94

0.95

300250200150100Po [W]

ηUg = 35V

Ug = 25V

fs = 100 kHz

27

IBF Converter with Voltage MultiplierIBF Converter with Voltage Multiplier

Ug U1

U2

+

+D2

D1

D3

S

ig

Ld Lm

im

Uo

+

-C1

C2

+C3 U3

Voltage multiplier cell

28

IBF Converter with Voltage MultiplierIBF Converter with Voltage Multiplier

Ug

U1

U2

+

+

D2

D1

D3

S

1:n21

ig

Ld

Lmim

Uo

+

-

Ls

is

C1

C2

ur+

Cr

x

Ug U1

U2

+

+D2

D1

D3

S

ig

Ld Lm

im

Uo

+

-C1

C2

+C3 U3

IBF converter with voltage multiplier cellIBF converter with voltage multiplier cellversus versus modified IBFmodified IBF

Similar behavior with a Similar behavior with a higher degree of freedomhigher degree of freedomin controlling the switch voltage stressin controlling the switch voltage stress

X

29

Converter WaveformsConverter Waveforms

BOOST section in BOOST section in DCMDCM and FLYBACK section inand FLYBACK section in CCMCCM

Ug U1

U3

+

+

D3

D1

D2

S

Np

Uo

+

-C1

C3

U2

+C2

Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

ig

im

iD1

iD2

iD3

t

t

tt

t0 t1 t3 t4 t6 t7=Ts-t0

ImpkIm1

Im2Imvl

Im1/n21

Im2/n21

Impk

t2 t5

Igpk

-is(t2)

is(t5)

iD3(t3)

30

5

10

15

20

25

0.4 0.5 0.6 0.7 0.81

2

3

4

5

Duty-cycle

M M1

Experimental PrototypeExperimental PrototypeDesign exampleDesign example:

Input voltage:Ug = 25÷35VOutput voltage: Uo = 400VNominal output power: Po = 300WSwitching frequency: fs = 100kHzBoost output: U1 = 75V Magnetizing inductance:Lm = 20µHPrimary leakage inductance:Ld = 0.4µHSecondary leakage inductance:Ls = 2µH

From the design constraints:

M= Uo / Ug=400/35=11.42 M1= U 1/ Ug=75/35=2.143

Numerically solving:

d = 0.519, n21 = 4.589 M2 = U 2/ Ug = 4.823 M3 = M-M1-M2 = U 3/ Ug = 4.454

Based on desired current ripple and DCM-CCM mode at nominal power

150V rated mosfet calculated voltage gains (continuous

curves) and simulation results (dotted)

31

Experimental resultsExperimental results

ig

uDS

ux

t0 t1 t2

ig

uDS

ux

t0 t1 t2

ig

uDS

ux

t3 t4 t5

ig

uDS

ux

t6

ux: 100V/div; uDS: 20V/div; ig: 5A/div

Measured main waveforms in a switching period Ug = 35V, Vo = 400V, Po = 300W

Details of turn on and turn off intervals

Ug U1

U3

+

+

D3

D1

D2

S

Np

Uo

+

-C1

C3

U2

+C2

Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

zero current turn on

layout stray

inductances resonance

32

Converter efficiencyConverter efficiency

Fig.1 Fig.2

Efficiency Efficiency

The converter efficiency was measured as a function of input voltage, at Po=300W,Fig.1, and at Ug=[25V,35V] and variable

output power, Fig. 2

25 27 29 31 33 35Ug [V]

0.93

0.94

0.95

η

0.93

0.94

0.95

0.96Ug = 35V

Ug = 25V

300250200150100Po [W]

η

33

Isolated IBF ConverterIsolated IBF Converter

Ug

U1

ur

+

+

SAC

D1

D2

Np

Uo

+

-

C1

Cr U2

+C2

Ns

Ld

Lm

ig

imis

id

S

CAC+

io

LsRo

UAC

Ug U1

U3

+

+

D3

D1

D2

S

Np

Uo

+

-C1

C3

U2

+C2

Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

For For isolationisolation, the loss, the loss--less less snubbersnubber DD11--CC11 is is substituted by an substituted by an

active clampactive clamp

34

Isolated IBF ConverterIsolated IBF Converter

Advantages:Advantages:

•• ZVS turn on ZVS turn on

•• Soft diode turn offSoft diode turn off

•• Reduces switch voltage stressReduces switch voltage stress

•• Clean diode voltage waveforms without parasitic Clean diode voltage waveforms without parasitic oscillationsoscillations

•• Energy transfer toward the output also during Energy transfer toward the output also during switch turn on intervalswitch turn on interval

•• Reduced active clamp circulating currentReduced active clamp circulating current

35

Converter OperationConverter Operation

Interval T01 = t1-t0

id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t

tt0 t1 t3 t4 t6=Ts-t0

Impk

Imvl

t2 t5

im(t0)

Ug

U1

+

Np

Uo

+

-

C1

U2

+C2

Ns

Ld

Lm

ig

imis

id

S

io

LsRo

D2

Soft DSoft D22 turn offturn off

Hp: negligible capacitor voltage ripples

36



id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

Ug

U1

ur

+

+

Np

Uo

+

-

C1

Cr U2

+C2

Ns

Ld

Lm

ig

imis

id

S

io

LsRo


37



Note: actual iD1 slope can be either positive or negativeNote: actual iD1 slope can be either positive or negative

id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

Ug

U1

+D1

Np

Uo

+

-

C1

U2

+C2

Ns

Ld

Lm

ig

imis

id

S

io

LsRo


38



id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

U1

+

SAC

D1

Np

Uo

+

-

C1

U2

+C2

Ns

Ld

Lmim

is

id

CAC+

io

LsRo

UAC

Soft DSoft D11 turn offturn off


39



id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

U1

ur

+

+

SAC

Np

Uo

+

-

C1

Cr U2

+C2

Ns

Ld

Lmim

is

id

CAC+

io

LsRo

UAC

Reduced active clamp circulating currentReduced active clamp circulating current


40


id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)



U1

+

SAC

D2

Np

Uo

+

-

C1

U2

+C2

Ns

Ld

Lmim

is

id

CAC+

io

LsRo

UAC

41

Converter ParametersConverter Parameters

• Input voltage: Ug = 25-35 V

• Output voltage: Uo = 400 V

• Nominal output power: Po = 300 W

• Switching frequency: fs = 100 kHz

• Magnetizing inductance: Lm = 20 µH

• Primary leakage inductance: Ld = 0.4 µH

• Secondary leakage inductance:Ls = 2 µH

42

id [5A/div]

uDS [20V/div]

uD1 [100V/div]


Ug = 35 V, Uo = 400 V, Po = 300 W (2µs/div)

Peaking due to a small dip in the converter input voltage due to the fast current rise time

43

id [5A/div]

uDS [20V/div]

uD1 [100V/div]


Ug = 35 V, Uo = 400 V, Po = 300 W (2µs/div)

The resonant phase reduces the active clamp

circulating current}

44

id [5A/div]


Ug = 35 V, Uo = 400 V, Po = 300 W (2µs/div)

The resonant phase reduces the active clamp

circulating current}

Ug

ur

+

+

SAC

D1

D2

Uo

+

-

C1

Cr

+C2

Ld

Lm

S

CAC+Ls

Ro

UAC

390 pF external capacitor added

45

Detail of Main Switch Turn OnDetail of Main Switch Turn On

Ug = 35 V, Uo = 400 V, Po = 300 W

id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

t6 = t0 t1 t2

id [5A/div]

uDS [20V/div]

uD1 [100V/div]

Time scale: 500ns/div

46

Detail of Main Switch Turn OffDetail of Main Switch Turn Off

Ug = 35 V, Uo = 400 V, Po = 300 W

id(t0)

Ug

idim

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

t3t4 t5

id [5A/div]

uDS [20V/div]

uD1 [100V/div]

Time scale: 500ns/div

47

Zero Voltage Switching Zero Voltage Switching

id [5A/div]

uDS [20V/div]

uD1 [100V/div]

uGS [5V/div]

Detail of the main switch turn on (nominal output power)

[200ns/div]

48

Different Operating ModeDifferent Operating Mode

Ug = 25 V, Uo = 400 V, Po = 100 W

D1 turns off during the switch on interval

id [2A/div]

uDS [20V/div]

uD1 [100V/div]

U1

+

D2

Uo

+

-

C1

U2

+C2

Ld

Lmim

id io

Ro

D1

49


Po = 300 W

0.91

0.92

0.93

0.94

25 27 29 31 33 35Ug [V]

η

0.92

0.93

0.94

0.95

300250200150100

ηUg = 35V

Ug = 25V

Po [W]

Power stage only

50

CommentsComments

• There are different topologies presented in literature whose behavior is very similar to the Integrated Boost-Flyback converter.

• These topologies have a drawback of a discontinuous input current waveform, that make the use of such converters for higher power levels at least problematic.

• For high power applications, a continuous input current represents a very nice feature

High Step -up Ratio DC -DC Converter Topologiesantenor/pdffiles/High_Step_Up_Converters... · High Step -up Ratio DC -DC Converter Topologies P. Tenti, L. Rossetto , G. Spiazzi, S.

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