Transcript EPE352 DC-DC converter
POWER ELECTRONICS
CIRCUITS, DEVICES, AND APPLICATIONS
Eng.Mohammed Alsumady
4/29/2020 EPE 352 POWER ELECTRONICS DC-DC CONVERTERS 2
Step Down Converter
k
t T s
1
V s
)
kV S R
I V S
)
V
)
V kV S S
/
R
R k k V S
• Constant frequency operation •Variable frequency operation 4/29/2020 3
PWM Waveform Generation
v r
V r T t k
V cr V r
• which is also called the modulation voltage, M 4/29/2020 4
Step Down Operation with RL Load 4/29/2020 5
Step Down Operation with RL Load 4/29/2020 6
Modes of Operation
V S
1
Ri
1
For i t
L
0)
di
1
dt
I
1
i t
1
i t
1 1
I e
1
kT
)
E
V S
R
I
2
E
1
e
0
Ri
2
For i t
2 (
L di
2 0)
dt
I
2
E i t
2 ( )
I e
2
i t
2 ( 4/29/2020
t
2 (1
E R
1
e
I
3
I
3
I
1 7
At t
kT At t
Modes of Operation
I
2
I e
1
I
3
V S
R E
1
e
1
I e
2 /
E R
1
e
/
z
TR L
T
4/29/2020 8
Discontinuous Operation •
I
1 0 ( )
i t
1 (
At t
V S
R E
kT
1
e
kT
)
I
2
I
2
V S
R E
1
e
kz
t
2
L R ln
1
L R ln
1
RI
2
E V S
For a continuous load current
E
E
For I e e kz z
1 1 1 0
E V S which gives V R S
e kz e z
1 1 0
x
E V S
E R e kz e z
1 1 0 4/29/2020 1
e
kz
9
v L
L di dt
Step-Up Operation
V S t
1
L
• The average output voltage
v o
V S
L
I t
2
V S
1
t t
2 1
V S
1 1
k
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Step-Up Operation
V S
L di
1
dt i t
1 ( )
V S L t
I
1
For di
1
dt
0
V S
0
V S
L di
2
dt
E For di
2
dt
0
i t
2 ( )
V S
E
V S
L E t
I
2 • For controllable power 0
V S
E
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Step-Up Operation
V S I
2
L di
1
dt i t
1 ( )
V S L
i t
1 (
kT
)
V S L kT t
I
1
I
1 4/29/2020 12
Converter Classifications • 1 st Quadrant converter • 2 nd Quadrant converter • 1 st and 2 nd quadrant • 3 rd and 4 th quadrant • Four-quadrant 4/29/2020 13
1 st Quadrant Converter • Both the voltage and the current are positive 4/29/2020 14
2 nd Quadrant Converter •The voltage is positive and the current is negative 4/29/2020 15
2 nd Quadrant Converter 0
L di L dt
Ri L
E L
I e
1
At t
1
kT
E R
1
e
1
kT
)
L
I
2 4/29/2020
V S L
Ri
L
2
L I e
di L
E dt
V S
R E
1
e
At t I
1
V S R t
2 1
e
1
e
z
E R
L I
2
t
2 (1
V R S e
kz
e
z
1
e
z
I
E R
1 16
1 st and 2 nd Quadrant Converter • S 1 • S 4 and D 4 and D 1 4/29/2020 17
3 rd • S 3 • S 2 and 4 and D 2 and D 3 th Quadrant Converter 4/29/2020 18
Four Quadrant Converter 4/29/2020 19
Switching Mode Regulators 4/29/2020 • Buck Regulator • Boost Regulator • Buck-Boost Regulator •Cuk Regulator 20
4/29/2020 Buck Regulator 21
Buck Regulator
V a
kV S I S V k S
(1
k
)
kI a
V C
8
I fL fC
V k S
(1
k
) 8 2
f CL
• The critical values for a continuous inductor current and capacitor voltage (1
L c
2
f
1
k C c
16
Lf
2 4/29/2020 22
4/29/2020 Boost Regulator 23
Boost Regulator
V a
V C
1
V S
k
a
a I S V fC a
V S
1
I
a k
I k a fC V k S fL
• The critical values for a continuous inductor current and capacitor voltage
L c k
1 2
f C c k
2
fR
4/29/2020 24
4/29/2020 Buck-Boost Regulator 25
Buck-Boost Regulator
V a
1
kV S
k I S
1
kI a
k
V C
(
V a I V a a
V S
)
fC
I k a fC V k S fL
• The critical values for a continuous inductor current and capacitor voltage
L c C c k
1 2
f k
2
fR
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Cuk Regulator 4/29/2020 27
Cuk Regulator
V a
1
kV S
k I S
1
kI a
k
1
V C
1
V C
2
V k S
I
2
V k S fL
1
fL
2 (
V S V a I V S S
V a
) (1
k
)
fC
1 8
C L f
2 2 2
I kV S S
8
C L f
2 2 1 2
fC
1
k
4/29/2020 28
Cuk Regulator •The critical values for a continuous inductor current and capacitor voltage
L c
1
L
1
L c
2
L
2 1
k
1 2
kf
2
f
2
R C c
1
C
1
k
2
fR C c
2
C
2 1 8
fR
4/29/2020 29
4/29/2020 Rectified Fed Converter 30
Input Filter 4/29/2020 31
• Summary A dc-dc can convert a fixed dc voltage to a • variable dc voltage. A four-quadrant converter allows power flow to and from load. • Switching mode converter can produce output voltage higher and lower than the input voltage. • The rectifier fed boost converter is commonly used for unity power factor correction (UPFC). 4/29/2020 32