High Step Up Ratio DC DC Converters Part_I

8/13/2019 High Step Up Ratio DC DC Converters Part_I

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HighHigh

StepStep

--up Ratio DCup Ratio DC

--DCDC

Converter TopologiesConverter Topologies

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

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

Speaker: G.Speaker: G. SpiazziSpiazzi

Part IPart I


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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


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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 hundredwatts)

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

Why?Why?


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Example ofExample of MicroinverterMicroinverter

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

200-300Wsingle pv panel

Utility

grid

High Step-Up

DC-DC

Microinverterfor single panel

MicroinverterMicroinverterstructurestructure


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Simple Boost TopologySimple Boost Topology

( )

( )

( )oo

o

D2

o

LSD

R,U,dFd1

1

U

U

d1R

rdrd1r1

1

d1

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:

VoltageVoltage

conversion ratioconversion ratio(neglecting inductor

current ripple):


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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 ratioVoltage conversion ratio MM includingincludingconduction losses:conduction losses:

Mmax


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ConverterConverterefficiency:efficiency:

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.7

0.75

0.8

0.85

0.9

0.95

1

Ro

Duty-cycle

( ) ( )ooLi

Do

ii

oo

in

out R,U,dFd1MIU

IU

IU

IU

P

P=====


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Low Power ApplicationsLow Power Applications

Ug

U1

U2+

+

D2

D1S

1:n21ig

LdLmim

Uo

+

-

C1

C2

ExampleExample: integrated Boost-Flyback converter

It can be seen as aflyback converter with anon dissipative snubber:D1 and C1 deliver to the

output the energy stored

in the transformerleakage inductance Ld


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Integrated BoostIntegrated Boost--FlybackFlyback ConverterConverter

Ideal waveforms:Ideal waveforms:-- CCM operation ofCCM 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:n21ig

LdLmim

Uo

+

-C1

C2

iD2

iD1

Advantages:Advantages: ZCS turn onZCS turn on Soft diode turn offSoft diode turn off Reduced switchReduced switch

voltage stressvoltage stress


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Integrated BoostIntegrated Boost--FlybackFlyback ConverterConverter

Problems:Problems:

Parasitic oscillations at DParasitic oscillations at D22 turn off caused by itsturn off caused by its

capacitance Ccapacitance Crr resonating with transformer leakageresonating with transformer leakageinductances Linductances Ldd and Land Lss

High voltage stressacross D2Ug

U1

U2+

+

D2

D1S

1:n21ig

LdLmim

Uo

+

-

Ls

is

C1

C2

ur+Cr

Dissipative R-C-D snubberis needed


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Modified IBF ConverterModified IBF Converter

Clamping diode D3 added to

the original topologyAdvantages:Advantages:

Clean diode voltageClean diode voltage

waveforms without parasiticwaveforms without parasiticoscillationsoscillations

Energy transfer toward theEnergy transfer toward theoutput also during switch turnoutput also during switch turn

on intervalon interval Slight voltage gain increaseSlight voltage gain increasedue to resonances betweendue to resonances between

parasitic componentsparasitic components

Ug

U1

U2+

+

D2

D1

D3

S

1:n21ig

LdLmim

Uo

+

-

Ls

is

C1

C2

ur+

Cr

x


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Interval T01 = t1-t0ig

im

iD1

iD2

iD3

t

t

t

t

t0t1 t3 t4 t6 t7=Ts-t0t2 t5

Ug

U1

U2+

+

D2

S

ig

LdLmim

Uo

+

-

Ls

C1

C2

iD2


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im

iD1

iD2

iD3

t

t

t

t


Ug

U1

U2+

+S

ig

LdLmim

Uo

+Ls

C1

C2

ur+

Cr

-


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im

iD1

iD2

iD3

t

t

t

t


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

LdLmim

Uo

+Ls

iD3

C1

C2

-


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im

iD1

iD2

iD3

t

t

t

t


Ug

U1

U2+

+D

1

D3

S

ig

LdLmim

Uo

+Ls

iD1C1

C2

-

iD3


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im

iD1

iD2

iD3

t

t

t

t


Ug

U1

U2+

+

D2

D1

ig

LdLmim

Uo

+Ls

C1

C2

-

iD1

iD2


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im

iD1

iD2

iD3

t

t

t

t


U1

U2+

+

D2Lmim

Uo

+Ls

C1

C2

-

iD2


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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 H

Primary leakage inductance: Ld

= 0.4 H

Secondary leakage inductance: Ls = 2 H


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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

UUM =

Comparison between calculations and spicesimulations

This unmatched pointcorresponds to adifferent topological

sequence


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Voltage Conversion RatioVoltage Conversion Ratio

g

o

UUM =

Effect of resonant intervals on the overallvoltage gain

0.4 0.45 0.5 0.55 0.6 0.65 0.76

7

8

9

10

1112

13

14M

Duty-cycle

No parasiticcomponents

With parasitic

components


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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 converterinput voltage due to fast current rise time


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

ig

im

iD1

iD2

iD3

t

t

t

t

t0t1 t3 t4 t6 t7=Ts-t0

Impk

t2 t5

t0 t1 t2

ig

uDS

ux

t3t4t5

ig

uDS

ux

t6


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Measured EfficiencyMeasured Efficiency

Po = 300 W

0.92

0.93

0.94

0.95

25 27 29 31 33 35

Ug[V]

fs= 100kHz

fs= 200kHz

0.90

0.91

0.92

0.93

0.94

25 27 29 31 33 35

Ug[V]

fs= 200kHz

fs= 100kHz

Po

= 200 W


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0.92

0.93

0.94

0.95

300250200150100

Po[W]

Ug= 35V

Ug= 25V

fs = 100 kHz


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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


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IBF Converter with Voltage MultiplierIBF Converter with Voltage Multiplier

Ug

U1

U2+

+

D2

D1

D3

S

1:n21ig

LdLmim

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 cellversusversus modified IBFmodified IBF

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

X


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Converter WaveformsConverter Waveforms

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

Ug U1

U3+

+

D3

D1

D2

S

NpUo

+

-C

1

C3

U2+

C2Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

ig

im

iD1

iD2

iD3

t

t

t

t

t0t1 t3 t4 t6 t7=Ts-t0

ImpkIm1

Im2Imvl

Im1/n21

Im2/n21

Impk

t2 t5

Igpk

-is(t2)

is(t5)

iD3(t3)


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5

10

15

20

25

0.4 0.5 0.6 0.7 0.8

1

2

3

4

5

Duty-cycle

M M1

Experimental PrototypeExperimental PrototypeDesign exampleDesign example:

Input voltage:Ug = 2535V

Output voltage:Uo = 400VNominal output power:Po = 300WSwitching frequency:

fs = 100kHzBoost output:U1 = 75VMagnetizing inductance:Lm = 20H

Primary leakage inductance:Ld = 0.4HSecondary leakageinductance:Ls = 2H

From the design constraints:

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

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

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

150V rated mosfet calculated voltagegains (continuous

curves) and simulationresults (dotted)


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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 mainwaveforms in aswitching periodUg = 35V, Vo = 400V,P

o

= 300W

Details of turn on andturn off intervals

Ug U1

U3

+

+

D3

D1

D2

S

NpUo

+

-C1

C3

U2+

C2Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

zero currentturn on

layoutstray

inductancesresonance


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Converter efficiencyConverter efficiency

Fig.1 Fig.2

Efficiency Efficiency

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

output power, Fig. 2

25 27 29 31 33 35U [V]

0.93

0.94

0.95

0.93

0.94

0.95

0.96 Ug= 35V

Ug= 25V

300250200150100Po[W]


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Isolated IBF ConverterIsolated IBF Converter

Ug

U1

ur+

+

SAC

D1

D2

Np

Uo+

-

C1

Cr U2+

C2

Ns

Ld

Lm

ig

im

is

id

S

CAC+

io

LsRo

UAC

Ug U1

U3+

+

D3

D1

D2

S

NpUo

+

-C1

C3

U2+

C2Ns

Ld Lm

ig im

is

Cr

Ls

+ur

x

ForFor isolationisolation, the loss, the loss--lessless snubbersnubber DD11--CC11 isis

substituted by ansubstituted by anactive clampactive clamp


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Isolated IBF ConverterIsolated IBF Converter

Advantages:Advantages:

ZVS turn onZVS turn on

Soft diode turn offSoft diode turn off

Reduces switch voltage stressReduces switch voltage stress

Clean diode voltage waveforms without parasiticClean diode voltage waveforms without parasiticoscillationsoscillations

Energy transfer toward the output also duringEnergy transfer toward the output also duringswitch turn on intervalswitch turn on interval

Reduced active clamp circulating currentReduced active clamp circulating current


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Converter OperationConverter Operation

Interval T12 = t2-t1

id(t0)

Ug

id

im

iSAC

iD2

iD1

t

t

t

tt0 t1 t3 t4 t6=Ts-t0

Impk

Imvl

t2 t5

im(t0)

Ug

U1

ur+

+

Np

Uo

+

-

C1

Cr U2+

C2

Ns

Ld

Lm

ig

im

is

id

S

io

Ls Ro

Hp: negligible capacitor voltage ripples


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

id(t0)

Ug

id

im

iSAC

iD2

iD1

t

t

t


Impk

Imvl

t2 t5

im(t0)

Ug

U1+

D1

Np

Uo

+

-

C1

U2+

C2

Ns

Ld

Lm

ig

im

is

id

S

io

LsRo



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id(t0)

Ug

id

im

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



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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

C PC t P t


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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 H

Primary leakage inductance: Ld = 0.4 H Secondary leakage inductance: Ls = 2 H

E i t l R ltE i t l R lt


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id[5A/div]

uDS[20V/div]

uD1[100V/div]


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

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

E i t l R ltE i t l R lt


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id[5A/div]

uDS[20V/div]

uD1[100V/div]


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

The resonant phasereduces the active clamp

circulating current}

E i t l R ltEx im t l R s lts


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id[5A/div]


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

The resonant phasereduces the active clamp

circulating current}

Ug

ur+

+

SAC

D1

D2

Uo

+

-

C1

Cr+

C2

Ld

Lm

S

CAC+Ls

Ro

UAC

390 pF externalcapacitor added

D t il f M i S it h T ODetail of Main Switch Turn On


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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

t


Impk

Imvl

t2 t5

im(t0)

t6= t0t1 t2

id[5A/div]

uDS[20V/div]

uD1[100V/div]

Time scale: 500ns/div

Detail of Main Switch Turn OffDetail of Main Switch Turn Off


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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

t


Impk

Imvl

t2 t5

im(t0)

t3t4t5

id[5A/div]

uDS[20V/div]

uD1[100V/div]

Time scale: 500ns/div

Zero Voltage SwitchingZero Voltage Switching


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Zero Voltage SwitchingZero 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]

Different Operating ModeDifferent Operating Mode


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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



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Po = 300 W

0.91

0.92

0.93

0.94

25 27 29 31 33 35

Ug[V]

0.92

0.93

0.94

0.95

300250200150100

Ug= 35V

Ug= 25V

Po[W]

Power stage only


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High Step Up Ratio DC DC Converters Part_I