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Six Basic DC/DC Converters Presented by Xinbo Ruan Aero-Power Sci-tech Center Nanjing University of Aeronautics & Astronautics
Transcript of Six Basic DC/DC Converters - ruanxb.nuaa.edu.cnruanxb.nuaa.edu.cn/Home/Ruan...
Six Basic DC/DC Converters
Presented by
Xinbo Ruan
Aero-Power Sci-tech CenterNanjing University of Aeronautics & Astronautics
Power Converters
1. DC/DC2. DC/AC3. AC/DC4. AC/AC
DC-DC Converters
NonNon--Isolated DCIsolated DC--DC Converter: singleDC Converter: single--switch, dualswitch, dual--switch, switch, and fourand four--switchswitch◎Single-switch: Buck, boost, buck-boost, Cuk, Zeta, and SEPIC;◎Dual-switch: Dual-switch buck-boost;◎Four-switch: Full-bridge converter.
Isolated DCIsolated DC--DC Converter: SingleDC Converter: Single--Switch, DualSwitch, Dual--Switch, Switch, and Fourand Four--SwitchSwitch◎Single-switch: Forward, Flyback;◎Dual-switch: Forward, Flyback;◎Four-switch: Full-bridge converter.
QVin
RLd
Vo
+
_
Linear DC Converter
Vin = 100 V
Vo = 50 V
Io = 10 A
η = VoIo / VinIo = Vo / Vin
= 50 / 100 = 50%
PQ = VQ IQ = 50 10 =500 (W)
Specifications:
Too LowEfficiency!!!
VQ = 100−50 =50 (V)
Switching-Mode DC Converter
Vin = 100 V
Vo = 50 V
Io = 10 A
Specifications:
HighEfficiency!!!
onT sT
bevt
t
vo100V
050V
Q on: PQ(on) = Vces Io ≅ 0
Q off: PQ(off) = Vin Iceo ≅ 0
η ≅ 100%
Ploss ≅ 0QVin
RLd
Vo
+
_
filter the high-frequency contentfreewheel diode
QVin
RLd
Vo
+
_
Lf
Cf
Derivation of Buck Converter
D
Operation Principle of Buck Converter: CCM
cfi
onT sT0
ov
bev
Lfi
Qi
maxLfi
minLfi
maxLfi
maxLfi
oI
Lv
minLfi
DiminLfi
QΔ
oV
oV−oin VV −
offT
t
t
t
t
t
t
t
Vo / Vin = D
Q ON
Q OFF
QVin
Lf
Cf
RLd
Vo
+
_
QVin
Lf
Cf
RLd
Vo
+
_
Operation Principle of Buck Converter: DCM
Q ON
Q OFF
Q OFF
cfi
onT sT0
ov
bev
Lfi
Di
Qi
Lv
'offT
disT
QΔ
oV
maxLfi
oV−oin VV −
maxLfi
maxLfi
t
t
t
t
t
t
t
QVin
Lf
Cf
RLd
Vo
+
_
QVin
Lf
Cf
RLd
Vo
+
_
QVin
Lf
Cf
RLd
Vo
+
_
Voltage Conversion Ratio
in
o
VV
0.0
0.1=yD
0.75
0.5
0.25
0.75
0.5
1.0
0.25
1.0 2.0 maxoG
o
II
CCM
DCM
Vin = Const
Q1Vin
Lf
Cf
RLd
Vo
+
_D2
Q2
D1
Buck Converter with Bi-Direction Switches
iQ2
0
maxLfit
t
t
t
iQ1
iD2
Q1 Q1Q1
iLf iLfmax
Ts 2Ts 3Ts
Q2
Buck Converter with Bi-Direction Switches
Q1 OFF;Q2 ON.
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
0
maxLfit
t
t
t
iQ1
iD2
Q1 Q1Q1
iLf iLfmax
Ts 2Ts 3Ts
iQ2
Q2
Buck Converter with Bi-Direction Switches
Q1 ON(D1 Conduct);Q2 OFF.
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
iQ2
0
maxLfit
t
t
t
iQ1
iD2
Q1 Q1Q1
iLf iLfmax
Ts 2Ts 3Ts
Q2
Buck Converter with Bi-Direction Switches
Q1 ON;Q2 OFF.
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
0
maxLfit
t
t
t
iQ1
iD2
Q1 Q1Q1
iLf iLfmax
Ts 2Ts 3Ts
iQ2
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
Q2
Buck Converter with Bi-Direction Switches
Lb
Q
D RLd
Vo
+
_Vin Cf
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
Buck Converter with Bi-Direction Switches
0
t
t
t
t
iQ1
iD1
iD2
iQ2
Q1 Q1
iLf
Ts 2Ts
Q2 Q2
Power Flow
QVin
Lf
Cf
RLd
Vo
+
_
Lb
Q
D RLd
Vo
+
_Vin Cf
Q1Vin
Lf
Cf
RLd
Vo
+
_Q2
D1
D2
Voltage Conversion Ratio of Boost Converter
o
in
V DV
=
o
in
V DV
=
1in
o
V DV
= −
D is the duty cycle of Q1
D is the duty cycle of Q1
D is the duty cycle of Q2
11
o
in
VV D
=−
Lb
Q
D RLd
Vo
+
_Cf
QVin
Lf
Cf
RLd
Vo
+
_
Lb
Q
D RLd
Vo
+
_Vin Cf
Vo < Vin Vo > Vin
1
21o
in
V DV D
=−
Why Buck-Boost Converter?
Lb
Q
D RLd
Vo
+
_Cf
QVin
Lf
Cf
Lc
Simplification of Buck-Boost Converter (1)
Q1
Vin
Lc
RLd
Vo
+
_
CfQ2D1
D2
Q1
VinLc
RLd
Vo
_
+
Cf
Q2D2
D1
Q1
Vin
Lc
RLd
Vo
+
_
CfQ2D1
D2
Q1
VinLc
RLd
Vo
+
_
Cf
Q2D1
D2
Q1
VinLc
RLd
Vo
_
+Cf
D1
Simplification of Buck-Boost Converter (2)
Lb
Q
D RLd
Vo
+
_Vin Cf
QVin
Lf
Cf
RLd
Vo
+
_
1
21o
in
V DV D
=−
How to get Cuk?
Q
Lf
Cf
RLd
Vo
+
_
Lb
Q
D
Vin Cf
Vin
Lb Vcb+ _
Cb
Q1 D1
Q2
Vin
Lf RLd
Vo
+
_Cf
D2
Q2
Vin
LfRLd
Vo
+
_
CfD2
镜像翻转
Derivation of Cuk
1cb
in
V DV D
=−
1o inDV V
D=
−1
1 inD DV
D⎛ ⎞= +⎜ ⎟−⎝ ⎠
1in inDD V V
D⎛ ⎞= +⎜ ⎟−⎝ ⎠
Negative output voltage Positive output voltage
Derivation of Zeta
Q1
VinLc Vo
_
+Cf
D1 RLd
Derivation of SEPIC
1cb
in
V DV D
=−
1o inDV V
D=
−1
1 in inV VD
= −−
Negativeoutput voltage
Positiveoutput voltage
Vin
Lb RLd
Vo
+
_Cf
Q2
D2
Q1
Vin
Lc Vo
+
_Cf
D1
QVin
Lf
Cf
RLd
Vo
+
_
Q1
Vin
Lc
RLd
Vo
_
+
Cf
D
Comparison of the Six Converters
Buck
Boost
Buck-Boost
Cuk
Zeta
Sepic
Converter
1o
in
V DV D
=−
1o
in
V DV D
=−
1o
in
V DV D
=−
1o
in
V DV D
=−
11
o
in
VV D
=−
o
in
V DV
=
Voltage Conversion
Ratio
Output Voltage Polarity
Input Current Ripple
Output Current Ripple
+
+
+
+
_
_
Large Small
Configu-ration
Simple
Simple
Simple
Complex
Complex
Complex
Large Large
Large
Large
Small
Small
Small
Small
Small
Large
Lb
Q
D RLd
Vo
+
_Vin Cf
Lf
Cf
RLd
Vo
_
+
Lb
QVin
Cb
D
Lf
CbLb
QVin
RLd
Vo
+
_Cf
D2
Q1
Vin
Lc
Cf
D
Lf
Cf
RLd
Vo
+
_
_ +Vo
vD
+
_
Topology
Thanks for your attention !
Questions? / Answer!
