Chapter 8 Switching Power Supplies
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1
Chapter 8
Switching Power Supplies
“Introduction to Modern Power Electronics”, 2nd Ed., John Wiley 2010by
Andrzej M. Trzynadlowski
Chapter 8 2
Buck converter
Fig. 8.1
L
C
i
iV vD
L
iD iCio
vo
i i
Chapter 8 3
Voltage and current waveforms in a buck converter
Fig. 8.2
t
t
t
t
t
i L
i
vDVi Vo
dTsw Tsw
iDC
i i
oI
Chapter 8 4
Waveforms of the capacitor current and output voltage in a buck converter
Fig. 8.3
IL QiC
Vo
2-T
C
B
A
vo
t 0
Chapter 8 5
Boost converter
Fig. 8.4
iV
L
vS C
vo
io
iC
iD
iS
i i
Chapter 8 6
Voltage and current waveforms in a boost converter
Fig. 8.5
t
t
t
I i
t
t
vs
dTsw Tsw
iD
si
iC
V iVo
i i
Chapter 8 7
Waveforms of the capacitor current and output voltage in a boost converter
Fig. 8.6
Q
Vo
Io DT
iC
T
C B
A
vo
t 0
Chapter 8 8
Impact of the inductor resistance on the voltage gain of a boost converter
Fig. 8.7
DUTY RATIO
0.5 0.6 0.7 0.8 0.9 1.0
VO
LTA
GE
GA
IN
0
5
10
15
20
25
rL=0
.001
r L=0
rL=0.005
rL=0.01
Chapter 8 9
Buck-boost converter
Fig. 8.8
iV
i i
v
L C
iC
io
vo
iL
L
iD
Chapter 8 10
Voltage and current waveforms in a buck-boost converter
Fig. 8.9
t
t
t
I
t
dTsw Tsw
iD
i
iC
i
Vt
Voi
vL
i
L L
Chapter 8 11
uk converter
Fig. 8.10
vS
iV
i i
vo
io
L 1 LC 1
iS
C
iD iC2
2
iC1
vD
vC1vL2
L22 i
Chapter 8 12
Waveforms of voltage and current in a uk converter
Fig. 8.11
t
iDt
iC2
t
Dvt
Vo
Vi
vS
dTsw Tsw
t
iS
Ii L2 o
iC1
t
t
Ii i i
Chapter 8 13
SEPIC (a) and Zeta (b) converters
Fig. 8.12
vS
iV
i i
vo
io
L 1 C 1
iS
C
iC2
2
iC1
L 2
iD
C
iV
i i
vo
io
1
iC2
iC1
L 1 C 2
vS L 2
i L2
i L1 iD
i L2
vD
(a)
(b)
Chapter 8 14
Voltage and current waveforms in SEPIC and Zeta converters
Fig. 8.13
t
iC1
t
IiL2 o
t
t
vS
dTsw Tsw
Vi Vo+
t
t
t
Ii i i
iD
Si
Chapter 8 15
Voltage and current waveforms in SEPIC and Zeta converters
Fig. 8.13
t
iC1
t
IiL2 o
t
t
vS
dTsw Tsw
Vi Vo+
t
t
t
Ii i i
iD
Si
Chapter 8 16
Vorperian’s switch model
Fig. 8.14
A C
P
d iC
d vAPvAP
0 V iC
Chapter 8 17
Averaged models of switched-mode dc-to-dc converters with Vorperian’s switch model: (a) buck, (b) boost, (c) buck-boost, (d) uk
Fig. 8.15
V SM
V SM V SM
V SM
A C
P
(a) (b)
(c ) (d)
A
C P
A P
C
C
A P
Chapter 8 18
Waveforms of the output voltage and current in a buck converter: solid lines – actual converter, dashed lines – averaged model
Fig. 8.16
io
vo
t 0
Chapter 8 19
Equivalent circuits of a transformer: (a) ideal transformer, (b) transformer with the magnetizing inductance included
Fig. 8.17
N 1
i
v1
v2
2
N 2 N 1
v1
v2
N 2
i 2
i 1
i 1 i'2
im
L m
(a)
(b)
20
Forward converter
Chapter 8
Fig. 8.18
L
i i
iV
D 3 D 1
3
1N
N
2N
D 2
io
voC
21
Flyback converter
Chapter 8
Fig. 8.19
2N
N 1 iV
i i
L m
D 1
vo
io
C
22
Isolated uk converter
Chapter 8
Fig. 8.20
iV
i i
L 1 C
2N
N 1
C
vo
io
C 2
11 12 L 2
23
Midpoint rectifier
Chapter 8
Fig. 8.21
v1
v i vo
24
Push-pull converter
Chapter 8
Fig. 8.22
i
N 1 N 2
D1
D3
D4
D2
L
C
Vi
i i
io
vo
S1
S2
25
Half-bridge converter
Chapter 8
Fig. 8.23
io
L
i i
iV
2N
1N
C 2
C 1 D1
D3 D4
D2
S1
S2
C vo
26
Full-bridge converter
Chapter 8
Fig. 8.24
io
L
2N
1N
C vo
i i
iV
D3
D4
S3
S4
D5 D6
S2
S1 D1
D2
27
Voltage-mode resonant switches: (a) L-type half-wave, (b) M-type half-wave, (c) L-type full-wave, (d) M-type full-wave
Chapter 8
Fig. 8.25
(a)
(c)
(b)
(d)
28
Current-mode resonant switches: (a) L-type half-wave, (b) M-type half-wave, (c) L-type full-wave, (d) M-type full-wave
Chapter 8
Fig. 8.26
(a)
(c )
(b )
(d )
29
Waveforms of the inductor current and capacitor voltage in an undamped resonant circuit
Chapter 8
Fig. 8.27
iL )t0 (
t0 t0
vC )(
iL
vC
t 0
30
Quasi-resonant ZVS buck converter with L-type half-wave switch
Chapter 8
Fig. 8.28
vo
io
iV
i i
L
C
L r
C r
31
Quasi-resonant ZCS boost converter with M-type full-wave switch
Chapter 8
Fig. 8.29
L
L r
C r C
i i
iV vo
io
32Chapter 8
TABLE 8.1 Comparison of the ZVS and ZCS Resonant-Switch Converters
______________________________________________________________________________
Property ZCS Converters ZVS Converters
____________________________________________________________________________________________________________________
Voltage gain
Buck converter kf 1 - kf
Boost converter 1/(1 - kf) 1/kf
Buck-boost converter kf /(1 - kf) 1/kf - 1
Control constant tON constant tOFF
variable tOFF variable tON
Waveform of voltage across the switch square sinusoidal
Waveform of current through the switch sinusoidal square
Load range 1 < r < ∞ 0 < r < 1
______________________________________________________________________________
33
Series-loaded resonant converter
Chapter 8
Fig. 8.30
i i
iV vo
io
r r
i r
v inv recv
1
2
C
C
L C
S1
S2
D1
D2
D3
D4
D5
D6
C
34
AC equivalent circuit of the series-loaded resonant converter
Chapter 8
Fig. 8.31
vrecvinv
L r rC ri
R eq
35
Control characteristic of the series-loaded resonant converter
Chapter 8
Fig. 8.32
36
Parallel-loaded resonant converter
Chapter 8
Fig. 8.33
i i
iV
r
vinv
1
2
C
C
L
S1
S2
D1
D2
D3
D4
D5
D6
vrecrC
i r
vo
io
C
L
37
AC equivalent circuit of the parallel-loaded resonant converter
Chapter 8
Fig. 8.34
vrecvinv
L r
R eq
i
C
rec
r
38
Control characteristic of the parallel-loaded resonant converter
Chapter 8
Fig. 8.35
39
Series-parallel resonant converter
Chapter 8
Fig. 8.36
i i
iV
r
1
2
C
C
L
S1
S2
D1
D2
vo
i o
D3
D4
D5
D6
C
C r2
C r1
ir
40
Control characteristic of the series-parallel resonant converter
Chapter 8
Fig. 8.37
41
Quasi-resonant ZCS buck converter with an L-type full-wave switch
Chapter 8
Fig. 8.38
iV
i i
L
C
io
vo
L r
C r
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