POWER ELECTRONICS
CIRCUITS, DEVICES, AND APPLICATIONS
Eng.Mohammed Alsumady
04/18/23 2
EPE 352POWER ELECTRONICS
DC-DC CONVERTERS
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Step Down Converter
11
( ) ( )
( ) /
ss
o average S o rms S
S S
o average S
tk t f
T
V kV V k V
V V RR
I kV R k
• Constant frequency operation
•Variable frequency operation
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PWM Waveform Generation
rr
cr
r
Vv t
TV
kV
• which is also called the modulation voltage, M
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Step Down Operation with RL Load
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Step Down Operation with RL Load
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Modes of Operation
22
2 2
/ /2 2
2 2 3 3 1
0
( 0)
( ) 1
( (1 ) )
tR L tR L
diRi L E
dtFor i t I
Ei t I e e
Ri t t k T I I I
11
1 1
/ /1 1
1 1 2
( 0)
( ) 1
( )
S
tR L tR LS
diV Ri L E
dtFor i t I
V Ei t I e e
Ri t t kT I
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Modes of Operation
/ /2 1
(1 ) / (1 ) /3 1 2
1
(1 ) 1
kTR L kTR LS
k TR L k kTR L
V EAt t kT I I e e
RE TR T
At t k T I I I e e zR L
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Discontinuous Operation
22 1
1 1 kzS
RILt ln
R E
V ELln e
R E
1
/1
1 1 2
2
0
( ) 1
( )
1
tR LS
kzS
I
V Ei t e
Ri t t kT I
V EAt t kT I e
R
• For a continuous load current
1
10 0
1
10
1
1
1
kzS
z
kz
zS
kz
zS
V e EFor I
R e R
e E
e V
E ewhich gives x
V e
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Step-Up Operation
1S
L
Vdiv L I t
dt L
• The average output voltage
1
2 2
1
1
1
o S S
S
tIv V L V
t t
Vk
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Step-Up Operation 1
1 1
1
( )
0 0
SS
S
VdiV L i t t I
dt Ldi
For Vdt
22 2
2
( )
0
SS
S
V EdiV L E i t t I
dt Ldi
For V Edt
• For controllable power
0 SV E
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Step-Up Operation 1
1 1
2 1 1
( )
( )
SS
S
VdiV L i t t I
dt LV
I i t kT kT IL
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Converter Classifications • 1st Quadrant converter
• 2nd Quadrant converter
• 1st and 2nd quadrant
• 3rd and 4th quadrant
• Four-quadrant
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1st Quadrant Converter • Both the voltage and the current are positive
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2nd Quadrant Converter •The voltage is positive and the current is negative
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2nd Quadrant Converter
/ /1
1 1 2
0
( ) 1
( )
LL
tR L tR LL
L
diL Ri E
dtE
i t I e eR
At t t kT i t t kT I
/ /2
2 2 1
(1 )
1 2
( ) 1
(1 ) ( (1 ) )
1
1 1
LS L
tR L tR LSL
L
k z kz zS S
z z
diV Ri L E
dtV E
i t I e eR
At t t k T i t t k T I
V Ve E e e EI I
R e R R e R
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1st and 2nd Quadrant Converter• S1 and D4
• S4 and D1
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18
3rd and 4th Quadrant Converter• S3 and D2
• S2 and D3
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Four Quadrant Converter
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Switching Mode Regulators
• Buck Regulator
• Boost Regulator
• Buck-Boost Regulator
•Cuk Regulator
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Buck Regulator
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Buck Regulator
2
(1 )
(1 )
8 8
a S S a
S
SC
V kV I kI
V k kI
fL
V k kIV
fC f CL
• The critical values for a continuous inductor current and
capacitor voltage
2
(1 )
2
1
16
c
c
k RL L
f
kC C
Lf
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Boost Regulator
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Boost Regulator
1 1
S a Sa S
a a S aC
a
V I V kV I I
k k fL
I V V I kV
V fC fC
• The critical values for a continuous inductor current and capacitor voltage
1
2
2
c
c
k k RL L
f
kC C
fR
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Buck-Boost Regulator
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Buck-Boost Regulator
1 1
( )
S a Sa S
a a aC
a S
kV kI V kV I I
k k fL
I V I kV
V V fC fC
• The critical values for a continuous inductor
current and capacitor voltage
1
2
2
c
c
k k RL L
f
kC C
fR
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Cuk Regulator
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Cuk Regulator
1 21 2
11 1
2 2 22 2 2 2
1 1
1
( )
(1 )
8 8
S aa S
S S
SS SC
S a
a SC
kV kIV I
k kV k V k
I IfL fL
I kI VV
V V fC fC
V k kVV
C L f C L f
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Cuk Regulator•The critical values for a continuous inductor
current and capacitor voltage
2
1 1
2 2
1 1
2 2
1
2
1
2
2
1
8
c
c
c
c
k RL L
kf
k RL L
f
kC C
fR
C CfR
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Rectified Fed Converter
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Input Filter
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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).