high step up ratio dc dc converters part_i
TRANSCRIPT
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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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Simple Boost TopologySimple Boost Topology
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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Simple Boost TopologySimple Boost Topology
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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Modified IBF ConverterModified IBF Converter
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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Modified IBF ConverterModified IBF Converter
Interval T12 = t2-t1ig
im
iD1
iD2
iD3
t
t
t
t
t0t1 t3 t4 t6 t7=Ts-t0t2 t5
Ug
U1
U2+
+S
ig
LdLmim
Uo
+Ls
C1
C2
ur+
Cr
-
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Modified IBF ConverterModified IBF Converter
Interval T23 = t3-t2ig
im
iD1
iD2
iD3
t
t
t
t
t0t1 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
LdLmim
Uo
+Ls
iD3
C1
C2
-
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Modified IBF ConverterModified IBF Converter
Interval T34 = t4-t3ig
im
iD1
iD2
iD3
t
t
t
t
t0t1 t3 t4 t6 t7=Ts-t0t2 t5
Ug
U1
U2+
+D
1
D3
S
ig
LdLmim
Uo
+Ls
iD1C1
C2
-
iD3
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Modified IBF ConverterModified IBF Converter
Interval T56 = t6-t5ig
im
iD1
iD2
iD3
t
t
t
t
t0t1 t3 t4 t6 t7=Ts-t0t2 t5
Ug
U1
U2+
+
D2
D1
ig
LdLmim
Uo
+Ls
C1
C2
-
iD1
iD2
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Modified IBF ConverterModified IBF Converter
Interval T67 = t7-t6ig
im
iD1
iD2
iD3
t
t
t
t
t0t1 t3 t4 t6 t7=Ts-t0t2 t5
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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Experimental ResultsExperimental Results
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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Measured EfficiencyMeasured Efficiency
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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Converter OperationConverter Operation
Interval T23 = t3-t2
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
tt0 t1 t3 t4 t6=Ts-t0
Impk
Imvl
t2 t5
im(t0)
Ug
U1+
D1
Np
Uo
+
-
C1
U2+
C2
Ns
Ld
Lm
ig
im
is
id
S
io
LsRo
Hp: negligible capacitor voltage ripples
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Converter OperationConverter Operation
Interval T34 = t4-t3
id(t0)
Ug
id
im
iSAC
iD2
iD1
t
t
t
tt0 t1 t3 t4 t6=Ts-t0
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
Hp: negligible capacitor voltage ripples
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Converter OperationConverter Operation
id(t0)
Ug
idim
iSAC
iD2
iD1
t
t
t
tt0 t1 t3 t4 t6=Ts-t0
Impk
Imvl
t2 t5
im(t0)
Hp: negligible capacitor voltage ripples
Interval T56 = t6-t5
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]
Experimental ResultsExperimental Results
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]
Experimental ResultsExperimental Results
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]
Experimental ResultsExperimental Results
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
t0 t1 t3 t4 t6=Ts-t0
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
t0 t1 t3 t4 t6=Ts-t0
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
Measured EfficiencyMeasured Efficiency
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Measured EfficiencyMeasured Efficiency
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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