Chapter 8 Switching Power Supplies

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