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Prac
tical
Desig
n of B
uck C
onve
rter
Dr. T
aufik
Asso
ciate
Profe
ssor
Elec
trical
Engin
eerin
g Dep
artm
ent
Califo
rnia
Polyt
echn
ic St
ate U
niver
sity,
USA
taufik
@ca
lpoly.
edu
http:/
/www
.ee.ca
lpoly.
edu/f
acult
y/tau
fik
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 2
Tuto
rial O
utlin
e•
Brie
f Rev
iew
of D
C-D
C C
onve
rter
•D
esig
n E
quat
ions
•Lo
ss C
onsi
dera
tions
•La
yout
Con
side
ratio
ns•
Effi
cien
cy Im
prov
emen
t•
Syn
chro
nous
Buc
k•
Res
onan
t Buc
k•
PW
M C
ontro
ller
•M
ultip
hase
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 3
Revie
w: D
C-DC
Con
verte
r Bas
ics
•A
circ
uit e
mpl
oyin
g sw
itchi
ng n
etw
ork
that
co
nver
ts a
DC
vol
tage
at o
ne le
vel t
o an
othe
r DC
vol
tage
•Tw
o ba
sic
topo
logi
es:
–N
on-Is
olat
ed•B
uck,
Boo
st, B
uck-
Boo
st, C
uk, S
EP
IC–
Isol
ated
•Pus
h-pu
ll, F
orw
ard,
Fly
back
, Hal
f-Brid
ge,
Full-
Brid
ge
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 4
Revie
w: D
C-DC
Con
verte
r Bas
ics
•W
hen
ON
: The
out
put v
olta
ge is
the
sam
e as
the
inpu
t vo
ltage
and
the
volta
ge a
cros
s th
e sw
itch
is 0
. •
Whe
n O
FF: T
he o
utpu
t vol
tage
is z
ero
and
ther
e is
no
curr
ent
thro
ugh
the
switc
h.•
Idea
lly, t
he P
ower
Los
s is
zer
o si
nce
outp
ut p
ower
= in
put
pow
er•
Per
iodi
c op
enin
g an
d cl
osin
g of
the
switc
h re
sults
in p
ulse
ou
tput
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 5
Revie
w: D
C-DC
Con
verte
r Bas
ics
•D
uty
Cyc
le ra
nge:
0 <
D <
1•
Two
way
s to
var
y th
e av
erag
e ou
tput
vol
tage
:–
Pul
se W
idth
Mod
ulat
ion
(PW
M),
whe
re to
n is
var
ied
whi
le th
e ov
eral
l sw
itchi
ng p
erio
d T
is k
ept c
onst
ant
–P
ulse
Fre
quen
cy M
odul
atio
n (P
FM),
whe
re to
n is
kep
t con
stan
t w
hile
the
switc
hing
per
iod
T is
var
ied
onon
st
Dutycycle
Dtf
T=
==
()0
00
11
TDT
oi
iV
vtdt
Vdt
VD
TT
==
=∫
∫
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 6
Revie
w: D
C-DC
Con
verte
r Bas
ics
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 7
Revie
w: D
C-DC
Con
verte
r Bas
ics
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 8
Revie
w: D
C-DC
Con
verte
r Bas
ics
Wan
ts:
DC
Vol
tage
and
DC
C
urre
nt
Sour
ce S
ide
Loa
d/U
ser
Side
DC
-DC
C
onve
rter
Wan
ts:
DC
Vol
tage
and
DC
C
urre
nt
Wan
ts:
No
AC
Com
pone
nt
No
Har
mon
ics
to s
witc
h
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 9
Revie
w: D
C-DC
Con
verte
r Bas
ics
Get
s:
Cur
rent
with
som
e ri
pple
Sour
ce S
ide
Loa
d/U
ser
Side
DC
-DC
C
onve
rter
Wan
ts:
Vol
tage
with
som
e ri
pple
Nee
ds F
ilter
ing
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 10
Wha
t is B
uck C
onve
rter?
•A
dc-
dc c
onve
rter c
ircui
t tha
t ste
ps d
own
a dc
vol
tage
at
its in
put
•N
on-is
olat
ed h
ence
idea
l for
boa
rd-le
vel c
ircui
try w
here
lo
cal c
onve
rsio
n is
nee
ded
–C
ell-p
hone
s, P
DA
s, fa
x m
achi
nes,
cop
iers
, sca
nner
s,
com
pute
rs, a
nyw
here
whe
n th
ere
is th
e ne
ed to
con
vert
DC
from
one
leve
l (ba
ttery
) to
othe
r lev
els
•W
idel
y us
ed in
low
vol
tage
low
pow
er a
pplic
atio
ns•
Syn
chro
nous
ver
sion
and
reso
nant
der
ivat
ives
pro
vide
im
prov
ed c
onve
rter’s
effi
cien
cy•
Mul
tipha
se v
ersi
on s
uppo
rts lo
w v
olta
ge h
igh
curr
ent
appl
icat
ions
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 11
The B
asic
Topo
logy
•Tw
o ty
pes
of C
ondu
ctio
n M
odes
–C
ontin
uous
Con
duct
ion
Mod
e (C
CM
) w
here
Indu
ctor
cur
rent
rem
ains
pos
itive
th
roug
hout
the
switc
hing
per
iod
–D
isco
ntin
uous
Con
duct
ion
Mod
e (D
CM
) w
here
Indu
ctor
cur
rent
rem
ains
zer
o fo
r so
me
time
in th
e sw
itchi
ng p
erio
d
Con
trolle
r
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 12
The B
asic
Topo
logy
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 13
Stea
dy S
tate
Ana
lysis
of C
CM B
uck:
Tra
nsfe
r Fun
ctio
n
•In
duct
or is
the
mai
n st
orag
e el
emen
t•
Tran
sfer
func
tion
may
be
deriv
ed fr
om V
olt S
econ
d B
alan
ce:
–Av
erag
e V
olta
ge a
cros
s In
duct
or is
Zer
o in
ste
ady
stat
e–
Indu
ctor
look
s lik
e a
shor
t to
a D
C
0L
Lonon
Loffoff
Vvt
vt
=+
=
•In
duct
or is
the
mai
n st
orag
e el
emen
t•
Tran
sfer
func
tion
may
be
deriv
ed fr
om V
olt S
econ
d B
alan
ce:
–Av
erag
e V
olta
ge a
cros
s In
duct
or is
Zer
o in
ste
ady
stat
e–
Indu
ctor
look
s lik
e a
shor
t to
a D
C
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 14
CCM
Buck
: Tra
nsfe
r Fun
ctio
n
•W
hen
the
switc
h is
clo
sed
orO
N–
Dio
de is
reve
rse
bias
ed s
ince
•C
atho
de (a
t Pos
itive
of I
nput
) mor
e po
sitiv
e th
an A
node
(at 0
vol
t)–
Vol
tage
acr
oss
indu
ctor
:–
Rec
all t
hat:
D =
t on/
T–
Then
, dur
atio
n of
on
time,
t on:
Lon
SO
vVV
=−
ontDT
=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 15
CCM
Buck
: Tra
nsfe
r Fun
ctio
n
•W
hen
the
switc
h is
OPE
N o
rOFF
–In
duct
or d
isch
arge
s ca
usin
g its
vol
tage
to re
vers
e po
larit
y–
Dio
de c
ondu
cts
sinc
e•
Ano
de (0
vol
t) is
mor
e po
sitiv
e th
an th
e C
atho
de (a
t so
me
nega
tive
volta
ge)
–V
olta
ge a
cros
s in
duct
or:
–R
ecal
l tha
t: t o
ff=
T –
t on =
T –
DT
Loff
Ov
V=−
()
1offt
DT
=−
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 16
CCM
Buck
: Tra
nsfe
r Fun
ctio
n 0Lonon
Loffoff
vt
vt
+=
0S
OO
OVDVDV
VD
−−
+=
OS
VDV
=
()
()(
)1
0S
OO
VV
DT
VDT
−+
−−
=
•A
vera
ge o
utpu
t vol
tage
is L
ES
S th
an In
put V
olta
ge
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 17
CCM
Buck
: Sizi
ng C
ompo
nent
s
For M
OS
FETs
: Vds
and
I d
Vrr
m, a
nd I f
C, V
and
I rm
s
L an
d I pk
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 18
CCM
Buck
: Ind
ucto
r Cur
rent
•W
hen
switc
h is
ON
, Ind
ucto
r is
char
ging
:
dtdiL
VV
vL
OS
L=
−=
SO
L
SO
Lon
on
SO
Lon
VV
di dtLV
Vi
tL
VV
iDT
L−=
=⊕
−Δ
=Δ
−Δ
=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 19
CCM
Buck
: Ind
ucto
r Cur
rent
•W
hen
switc
h is
OFF
, Ind
ucto
r is
disc
harg
ing:
LL
Odi
vV
Ldt
=−
=
()
1
OL
OLoff
off
OLoff
Vdi dt
L Vi
tL V
iDT
L
−=
=−
−Δ
=Δ
−Δ
=−
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 20
CCM
Buck
: Ind
ucto
r Cur
rent
•W
e ca
n th
en d
eter
min
e I Lm
inan
d I Lm
ax
00
max
01
1(1
)(1
)2
22
LL
L
iV
VD
II
DT
VR
LR
LfΔ
⎡⎤
−⎡
⎤=
+=
+−
=+
⎢⎥
⎢⎥
⎣⎦
⎣⎦
00
min
01
1(1
)(1
)2
22
LL
L
iV
VD
II
DT
VR
LR
LfΔ
⎡⎤
−⎡
⎤=
−=
−−
=−
⎢⎥
⎢⎥
⎣⎦
⎣⎦
Ave
rage
Indu
ctor
C
urre
nt =
Ave
rage
O
utpu
t Cur
rent
= V
o/R
LiΔ
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 21
Sizin
g In
duct
or: C
ritica
l Indu
ctan
ce
min
0m
ax1(1
)0
22
LL
LC
iD
II
VR
Lf
Δ⎡
⎤−
==
−=
−⎢
⎥⎣
⎦
•I Lm
in is
use
d to
det
erm
ine
the
Crit
ical
Indu
ctan
ce (M
inim
um
Indu
ctan
ce v
alue
at w
hich
the
indu
ctor
cur
rent
reac
hes
Bou
ndar
y C
ondu
ctio
n M
ode)
•A
ny in
duct
ance
low
er th
an c
ritic
al in
duct
ance
will
cau
se th
e bu
ck to
op
erat
e in
Dis
cont
inuo
us C
ondu
ctio
n M
ode
•R
equi
rem
ent i
s se
t eith
er b
y m
eans
of m
axim
um ∆
i Lor
by
spec
ifyin
g th
e m
inim
um p
erce
ntag
e lo
ad w
here
con
verte
r stil
l m
aint
ains
CC
M•
Set
I Lm
in=
0, th
en s
olve
for L
= L
C, t
hen
choo
se L
> 1
.05*
L C
Min
imum
Loa
d (o
utpu
t cur
rent
)
max
max
(1)
2C
DR
Lf
−=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 22
Sizin
g In
duct
or: C
ritica
l Indu
ctan
cem
axm
ax(1
)2
CD
RL
f−
=
Cal
cula
ted
at M
inim
um
Inpu
t Vol
tage
•C
alcu
late
d at
Min
imum
Out
put
Cur
rent
= R
max
= V
o/Iom
in
•Io
min
is e
ither
giv
en a
s pe
rcen
tage
of l
oad
to m
aint
ain
CC
M, e
.g. 1
0% lo
ad w
ith C
CM
•O
r, Io
min
is c
alcu
late
d as
sp
ecifi
ed b
y m
axim
um ∆
i L,
such
that
Iom
in =
∆i L/
2
•S
witc
hing
freq
uenc
y no
rmal
ly
chos
en b
y th
e de
sign
er•
The
high
er th
e sw
itchi
ng
frequ
ency
, the
sm
alle
r the
requ
ired
criti
cal i
nduc
tanc
e, i.
e. b
enef
icia
l fo
r red
ucin
g si
ze o
f Buc
k
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 23
Sizin
g In
duct
or: P
eak C
urre
nt
•I Lm
ax is
use
d to
det
erm
ine
peak
cur
rent
ratin
g of
Indu
ctor
•W
orst
cas
e m
axim
um in
duct
or c
urre
nt o
ccur
s at
max
imum
lo
ad
Max
imum
out
put p
ower
ratin
g pe
r spe
cifie
d re
quire
d ou
tput
vol
tage
min
max
0m
in
(1)
12
2L
LL
iD
II
VR
LfΔ
⎡⎤
−=
+=
+⎢
⎥⎣
⎦
Max
imum
Loa
d (o
utpu
t cur
rent
)
Cho
sen
indu
ctan
ce v
alue
as
disc
usse
d pr
evio
usly
Cal
cula
ted
from
H
ighe
st In
put
Vol
tage
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 24
Sizin
g Sw
itch:
Vol
tage
Rat
ing
•W
ith id
eal d
iode
, the
Vsw
itch-
max
= V
inm
ax
•Fo
r non
-idea
l dio
de, V
switc
h-m
ax=
Vin
max
+ V F
whe
re V
Fis
the
max
imum
forw
ard
drop
acr
oss
the
diod
e (c
alcu
late
d at
m
axim
um lo
ad c
urre
nt)
•U
se s
afet
y fa
ctor
of a
t lea
st 2
0%•
For M
OS
FET,
the
ratin
g w
ould
be
VD
Sm
ax
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 25
Sizin
g Sw
itch:
Cur
rent
Rat
ing
•S
witc
h cu
rren
t rat
ing
is c
alcu
late
d ba
sed
on a
vera
ge
valu
e•
Dra
w s
witc
h cu
rren
t wav
efor
m a
nd th
en c
ompu
te th
e av
erag
e va
lue
•B
y K
CL,
Indu
ctor
Cur
rent
= S
witc
h C
urre
nt +
Dio
de C
urre
nt•
Dur
ing
t ON, I
nduc
tor c
urre
nt e
qual
s sw
itch
curr
ent
•D
urin
g t O
FF, I
nduc
tor c
urre
nt e
qual
s di
ode
curr
ent
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 26
Switc
h Cu
rrent
Wav
efor
m
ON
ON
ON
OFF
OFF
OFF
i L
i Switc
h
i Dio
de
t t t
T2T
3T
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 27
Switc
h Cu
rrent
Wav
efor
m fo
r Cur
rent
Rat
ing
[]
()
()
max
max
max
22
2L
LL
LL
Switch
ii
iDT
ii
DI
T−Δ
+⋅
−Δ
⋅=
=⋅
max
max
max
Switch
oI
ID
−>
⋅
ON
ON
ON
i Switc
h
t
i Lmax
i Lmin
Ave
rage
Val
ue
T2T
0 ()
min
max
2L
Lon
Switch
ii
tI
T+
⋅=
⋅
max
2LSwitch
LL
oi
Ii
DID
ID
Δ⎛
⎞=
−=
⋅=
⋅⎜
⎟⎝
⎠
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 28
MOSF
ET R
atin
g Ex
ampl
e
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 29
Sizin
g Di
ode (
Scho
ttky)
: Vol
tage
Rat
ing
•K
now
n as
PIV
(Pea
k In
vers
e V
olta
ge) o
r VR
RM
is th
e m
axim
um v
olta
ge a
cros
s th
e di
ode
•W
ith id
eal s
witc
h, th
e V R
RM
= V
inm
ax
•Fo
r non
-idea
l dio
de, V
RR
M=
Vin
max
+ V
SW
whe
re V
SWis
the
max
imum
forw
ard
drop
acr
oss
the
switc
h (c
alcu
late
d at
m
axim
um lo
ad c
urre
nt)
•A
llow
at l
east
> 2
0% s
afet
y fa
ctor
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 30
Sizin
g Di
ode (
Scho
ttky)
: Cur
rent
Rat
ing
•S
ame
appr
oach
as
that
for t
he s
witc
h cu
rren
t
OFF
OFF
OFF
i Dio
de
tT
2T3T
Ave
rage
Val
ue
[]
()(
)(
)()
max
max
max
12
12
2L
LL
LL
F
ii
iDT
ii
DI
T−Δ
+⋅
−−Δ
⋅−
==
⋅
()
max
min
1F
oI
ID
>⋅
−
()
min
max
2L
Loff
F
ii
tI
T+
⋅=
⋅
()
()
11
FL
oI
ID
ID
=⋅
−=
⋅−
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 31
Scho
ttky D
iode
Rat
ing
Exam
ple
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 32
Sizin
g Ou
tput
Cap
acito
r: Vo
ltage
Rat
ing
•C
apac
itor V
olta
ge s
houl
d w
ithst
and
the
max
imum
out
put
volta
ge–
Idea
lly: V
cmax
= V
o+ ∆V
o/2–
Mor
e re
alis
tic: C
apac
itor h
as E
SR
(Equ
ival
ent S
erie
s R
esis
tanc
e) w
hich
wor
sens
∆V
o
–O
utpu
t vol
tage
ripp
le c
ontri
bute
d by
ES
R is
(ES
R *
∆I L)
–S
uppr
essi
ng ri
pple
con
tribu
tion
from
ES
R•
Red
uce
ES
R (P
aral
lelin
g C
aps,
Low
ES
R C
aps)
•R
educ
e ∆I
L by
incr
easi
ng L
or i
ncre
asin
g sw
itchi
ng fr
eque
ncy
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 33
Sizin
g Ou
tput
Cap
acito
r: Mi
nim
um C
apac
itanc
e
•Th
e A
C c
ompo
nent
(rip
ple)
of i
nduc
tor c
urre
nt fl
ows
thro
ugh
the
capa
cito
r, le
avin
g th
e av
erag
e flo
win
g th
roug
h th
e lo
ad•
Cap
acito
r cur
rent
wav
efor
m w
ill lo
ok li
ke:
ON
ON
ON
OFF
OFF
OFF
i C
tT
2T3T
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 34
Sizin
g Ou
tput
Cap
acito
r: Mi
nim
um C
apac
itanc
e
()
() 2
11
1 22
28
88
O
OL
L
VDT
DV
ii
TL
qArea
ff
Lf
−−
ΔΔ
⎛⎞
⎛⎞
=⋅Δ
==
==
⎜⎟ ⎜
⎟⎝
⎠ ⎝⎠
+Qi C
tT/
2
T
-Q
()
()
()
22
11
88
Oo
oo
oO
DV
Dq
qC
VC
VLf
VLf
VV
−−
=⋅Δ
⇒=
==
ΔΔ
Δ
()
()
min
218
oO
DC
LfVV
−=
ΔP
erce
nt V
opp
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 35
Sizin
g Ou
tput
Cap
acito
r: RM
S Cu
rrent
Rat
ing
ON
ON
ON
OFF
OFF
OFF
i C
tT
2T3T
i Lmax
–I o
= ∆i
L/2
()
12
33
23
Cpk
OL
Crms
iDV
ii
Lf−
Δ=
==
()
min
12
3O
Crms
DV
iLf
−=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 36
Sizin
g In
put C
apac
itor:
Volta
ge R
atin
g
•C
apac
itor V
olta
ge s
houl
d w
ithst
and
the
max
imum
inpu
t vo
ltage
–Id
eally
: Vcm
ax=
Vin
max
–M
ore
real
istic
: Cap
acito
r has
ES
R (E
quiv
alen
t Ser
ies
Res
ista
nce)
con
tribu
tes
to c
apac
itor l
oss
–M
inim
izin
g lo
ss c
ontri
butio
n fro
m E
SR
•R
educ
e E
SR
(Par
alle
ling
Cap
s, L
ow E
SR
Cap
s)
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 37
Sizin
g In
put C
apac
itor:
Mini
mum
Cap
acita
nce
ON
ON
ON
OFF
OFF
OFF
i C
tT
2T3T
i Lmax
–D
*IO
–D
*IO
()
()
11
Ooff
OO
DDI
qArea
tDI
DTDI
f−
⋅⋅
=⋅
=⋅
⋅=
−⋅
⋅=
()
()
11
O
Oin
inin
in
DDI
DDI
qf
qC
VC
VV
fV
−⋅
⋅−
⋅⋅
=⋅Δ
⇒=
==
ΔΔ
Δ
()
max
1O
in
DDI
CfV
−⋅
⋅=
Δ
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 38
Sizin
g In
put C
apac
itor:
RMS
Curre
nt R
atin
g
()
()2
2Crms
Switchrms
switchavg
II
I−
−=
−
ON
ON
ON
OFF
OFF
OFF
i C
tT
2T3T
i Lmax
–D
*IO
–D
*IO
()
2
21
2L
Crms
oo
oiI
ID
DI
I
⎛⎞
⎛⎞
⎡⎤
Δ⎜
⎟=
+−
⋅⎜
⎟⎢
⎥⎜
⎟⋅
⎜⎟
⎣⎦
⎝⎠
⎝⎠
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 39
To S
umm
arize (
)m
axm
in1
Fo
II
D>
⋅−
()
()
min
218
oO
DC
LfVV
−=
Δ ()
min
12
3O
Crms
DV
iL
−=
Vcm
ax=
Vo
+ ∆V
o/2V
RR
M =
Vin
max
Vsw
itch-
max
= V
inm
ax
max
max
max
Switch
oI
ID
−>
⋅
max
max
(1)
2C
DR
Lf
−=
min
max
0m
in
(1)
12
LD
IV
RLf
⎡⎤
−=
+⎢
⎥⎣
⎦
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 40
Sim
ple B
uck D
esig
n: 12
V to
2.5V
1A
ΔIL
0.19
8A
=Δ
IL1
D−
()
Vo
⋅L
f⋅:=
ILm
ax1.
099
A=
ILm
axIo
max
1D
−(
)V
o⋅
2L⋅
f⋅+
:=
L20
010
6−
H⋅
:=C
hoos
e:
Lcrit
1.97
910
4−
×H
=Lc
rit1
D−
()
2f⋅
Vo
Iocc
m⋅
:=
Indu
ctor
:
D0.
208
=D
Vo
Vs
:=So
lutio
n:
f50
kHz
:=%
Vo
1%:=
Iocc
m0.
1A:=
Iom
ax1A
:=V
o2.
5V:=
Vs
12V
:=G
iven
:
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 41
Sim
ple B
uck D
esig
n: 12
V to
2.5V
1A
%V
o0.
396
%=
%V
o1
D−
()
8L⋅
f2⋅
Co
⋅:=
Co
5010
6−
F⋅
:=C
hoos
e
C1.
979
105
−×
F=
C1
D−
()
8L⋅
f2⋅
1%
Vo
⋅:=
Vcm
ax2.
513
V=
Vcm
axV
o%
Vo
Vo
⋅ 2+
:=
Cap
acito
r:
If0.
792
A=
If1
D−
()
Iom
ax⋅
:=
Vrr
m12
V=
Vrr
mV
s:=
Dio
de:
Id0.
208
A=
IdD
Iom
ax⋅
:=
Vds
12V
=V
dsV
s:=
MO
SFET
:
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 42
Sim
ple B
uck D
esig
n: 12
V to
2.5V
1A R1 2.
5C
1 50u
0
V1
12D
brea
kD
1
L1 200u
12
V2
TD =
0
TF =
10n
PW
= {(
3.18
5/12
)*(1
/50k
)}P
ER
= {1
/50k
}
V1
= 0
TR =
10n
V2
= 1
+-
+
-
Sbr
eak
S1
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 43
Sim
ple B
uck D
esig
n: 12
V to
2.5V
1A
Time
3.6800ms
3.7000ms
3.7200ms
3.7400ms
3.7600ms
3.7800ms
3.8000ms
3.8182ms
-I(V1)
0A
1.0A
2.0A
Input Current
I(L1)
1.00A
1.25A
0.59A
SEL>>
Inductor Current
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 44
Non-
idea
l Buc
k: L
oss C
onsid
erat
ions
•W
hen
effic
ienc
y es
timat
ion
is re
quire
d in
the
desi
gn, l
osse
s in
Buc
k ci
rcui
t sho
uld
be
cons
ider
ed•
Sev
eral
maj
or lo
sses
to c
onsi
der:
–S
tatic
loss
of M
OS
FET
–S
witc
hing
loss
of M
OS
FET
–M
OS
FET
Gat
e D
rive
Loss
es
–S
tatic
loss
of d
iode
–S
witc
hing
loss
of d
iode
–In
duct
or’s
cop
per l
oss
–C
apac
itor’s
ES
R lo
ss
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 45
Stat
ic Lo
ss o
f MOS
FET
•W
ith M
OS
FET,
its
on re
sist
ance
RD
Son
dire
ctly
impa
cts
the
stat
ic lo
ss•
RD
Son
depe
nds
on a
pplie
d ga
te v
olta
ge a
nd M
OS
FET’
s ju
nctio
n te
mpe
ratu
re
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 46
Stat
ic Lo
ss o
f MOS
FET
•R
ecal
l, sw
itch
curr
ent:
ON
ON
ON
i Switc
h
t
i Lmax
i Lmin
Ave
rage
Val
ue
T2T
0
•S
tatic
loss
for M
OS
FET
with
RD
Son:
2static
switchrms
DSon
PI
R−
=⋅
2
12
Lstatic
oDSon
oiP
ID
RI
⎛⎞
⎛⎞
⎡⎤
Δ⎜
⎟=
+⋅
⎜⎟
⎢⎥
⎜⎟
⋅⎜
⎟⎣
⎦⎝
⎠⎝
⎠
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 47
Switc
hing
Los
s of M
OSFE
T•
The
switc
hing
loss
dep
ends
on
how
the
volta
ge a
nd c
urre
nt
over
laps
•M
ay b
e ap
prox
imat
ed w
ith a
sce
nario
whe
re v
olta
ge a
nd
curr
ent s
tart
mov
ing
sim
ulta
neou
sly
and
reac
h th
eir
endp
oint
s•
The
over
lap
caus
es p
ower
loss
(V x
I)•
Will
ass
ume
to o
ccur
bot
h at
turn
-on
and
turn
-off
trans
ition
s
t ont of
f
turn
on
turn
off
I oV
INI o
VIN
0
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 48
Switc
hing
Los
s of M
OSFE
T
()
6oin
switching
onoff
IVP
tt
T=
+
t ont of
f
turn
on
turn
off
I oV
INI o
VIN
0
()
6oinon
onIV
tPt
T=
()
6oinoff
off
IVt
Pt
T=
()
()
66oinoff
oinon
switching
onoff
IVt
IVt
PPt
Pt
TT
=+
=+
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 49
Switc
hing
Los
s of M
OSFE
T &
Gate
Driv
e Los
s
•W
hen
MO
SFE
T is
off,
its
outp
ut c
apac
itanc
e C
oss
is
bein
g ch
arge
d tra
nsla
tes
to lo
ss 2os
1 2C
sOSS
inP
CVf
=
•G
ate
driv
e lo
ss c
omes
from
the
tota
l gat
e ch
arge
Qga
tean
d th
e ga
te d
rive
volta
ge V
gate
used
1 2gate
gate
gate
PQ
Vf
=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 50
Stat
ic Lo
ss o
f Dio
de: F
orwa
rd L
oss
•Lo
sses
that
occ
ur d
urin
g di
ode’
s fu
lly o
n (fo
rwar
d lo
ss) a
nd fu
lly o
ff (r
ever
se lo
ss) c
ondi
tions
•Fo
rwar
d lo
ss c
ome
from
the
prod
uct o
f dio
de’s
fo
rwar
d vo
ltage
(VF)
and
forw
ard
curr
ent (
I F),
in
addi
tion
to th
e rm
s lo
ss d
ue to
dio
de d
ynam
ic
resi
stan
ce, r
d
2forward
ff
fd
PV
IIr
=⋅
+⋅
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 51
Stat
ic Lo
ss o
f Dio
de: F
orwa
rd L
oss
2forward
ff
fd
PV
IIr
=⋅
+⋅
()
1f
oI
DI
=−
⋅(
)2
2m
axm
inm
axm
in
13
f
DI
II
II
−⎡
⎤=
++
⋅⎣
⎦
From
dat
ashe
et
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 52
Stat
ic Lo
ss o
f Dio
de: R
ever
se L
oss
•Lo
ss o
ccur
s w
hen
the
diod
e is
in th
e fu
lly o
ff or
non
-co
nduc
ting
cond
ition
()
DI
VP
rr
reverse
−⋅
⋅=
1
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 53
Switc
hing
Los
s of D
iode
: Tur
n On
Los
s•
The
switc
hing
beh
avio
r at t
urn-
on is
cha
ract
eriz
ed b
y a
low
val
ue o
f pea
k fo
rwar
d vo
ltage
(VFP
) and
forw
ard
reco
very
tim
e (t f
r)
()
fI
tV
VP
ffr
fFP
ON
⋅⋅
⋅−
⋅=
4.0
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 54
Switc
hing
Los
s of D
iode
: Tur
n On
Los
s•
Bot
h V
FPan
d t fr
are
norm
ally
plo
tted
agai
nst d
I d(t)/
dt in
the
data
shee
t, w
here
as d
I d(t)/
dt it
self
is a
lso
avai
labl
e in
the
data
shee
t fo
r a g
iven
set
of c
ondi
tions
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 55
Switc
hing
Los
s of D
iode
: Tur
n Of
f Los
s•
Turn
-off
loss
con
stitu
tes
appr
ecia
ble
switc
hing
loss
es
due
to th
e ov
erla
ppin
g of
dio
de v
olta
ge a
nd c
urre
nt a
t tu
rn-o
ff w
ith it
s as
soci
ated
reve
rse-
reco
very
tim
e
()
() rr
brr
rrrrm
drra
rrm
d
tdtdI
dd
dsoff
tk
kI
Vt
IV
II
VP
rr
d
20
00
015.0
433
.046
7.0
033
.05.0
)(1
+−
++
=
()
)(10
rr
dt
dtdId
rrm
rra
II
t=
()
rra
rrrrb
tt
t−
⋅=
11.1
[]
rrb
rrrr
rrt
kt
t⋅
=3
2,
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 56
Indu
ctor
’s Co
pper
Los
s•
Indu
ctor
’s w
indi
ng is
mad
e of
cop
per a
nd h
ence
in
here
ntly
it w
ill h
ave
resi
stiv
e lo
ss
21
13
2L
Li
II
IΔ ⎛
⎞=
+⎜
⎟⎝
⎠
Ave
rage
In
duct
or
Cur
rent
, I
•W
ith in
duct
or’s
dc
resi
stan
ce o
f RL
and
indu
ctor
’s rm
s cu
rren
t, th
e co
pper
loss
of i
nduc
tor i
s:
2
LL
LP
IR
=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 57
Indu
ctor
’s Co
re L
oss
•Fa
ctor
s af
fect
ing
core
loss
: sw
itchi
ng fr
eque
ncy
F,
tem
pera
ture
, flu
x sw
ing
B•
Gen
eral
form
:
Cor
e Lo
ss =
Cor
e Lo
ss/U
nit V
olum
e x
Vol
ume
Whe
re,
Cor
e Lo
ss/U
nit =
k1
x B
k2x
Fk3
•C
onst
ants
k1,
k2,
and
k3
are
norm
ally
pro
vide
d by
the
core
man
ufac
ture
rs
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 58
Capa
citor
’s ES
R Lo
ss•
Rea
l wor
ld c
apac
itors
pos
ses
ES
R (E
quiv
alen
t Ser
ies
Res
ista
nce)
•E
SR
can
mea
sure
d w
ith, f
or e
xam
ple,
Cap
acito
r Wiz
ard
23L
Ci
IΔ
=
•Lo
ss d
ue to
Cap
acito
r’s E
SR
is:
2
ESR
CP
IESR
=
ON
ON
ON
OFF
OFF
OFF
i C
tT
2T3T
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 59
Buck
Des
ign
With
Los
ses
Buc
k D
esig
n w
ith L
osse
sTa
ufik
Max
imum
Out
put P
ower
:Po
max
120W
:=μ
110
6−
⋅≡
Nom
inal
Out
put V
olta
ge:
Von
om12
V:=
m1
103
−⋅
≡
Nom
inal
Inpu
t Vol
tage
:V
inom
24V
:=
Sw
itchi
ng F
requ
ency
:Fs
250k
Hz
:=
Min
imum
Per
cent
CC
M:
Iccm
10%
:=
Max
imum
Rip
ple
Per
cent
age:
Vop
p2%
:=
Des
ign
Cal
cula
tions
and
Siz
ing
Com
pone
nts:
Nom
inal
Dut
y C
ycle
:D
Von
omV
inom
0.5
=:=
Crit
ical
Indu
ctan
ce:
Lc1
D−
()
Von
om2
Iccm
Pom
ax⋅
⎛ ⎜ ⎝
⎞ ⎟ ⎠⋅
2Fs⋅
12.0
00Hμ⋅
=:=
Cho
ose
L >
LcLo
200μ
H:=
with
ass
umed
DC
resi
stan
ce o
f: R
Lo10
0mΩ
:=
Pea
k In
duct
or C
urre
nt:
ILop
kV
onom
1
Von
om2
Pom
ax
1D
−(
)2
Lo⋅Fs⋅
+⎡ ⎢ ⎢ ⎣
⎤ ⎥ ⎥ ⎦
⋅10
.06A
=:=
Sw
itch
Vol
tage
:V
swm
axV
inom
24V
=:=
Sw
itch
Cur
rent
:Id
DPo
max
Von
om⋅
5A=
:=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 60
Cho
ose
MO
SFE
T IR
F747
1 40
V 1
0A R
dson
13m
O
Dio
de V
rrm
:V
rrm
Vin
om24
V=
:=
Dio
de F
orw
ard
Cur
rent
:If
1D
−(
)Po
max
Von
om⋅
5A=
:=
Cho
ose
MB
R30
40
Cap
acito
r Vol
tage
Rat
ing:
Vca
pV
onom
Vop
pV
onom
⋅ 2⎛ ⎜ ⎝
⎞ ⎟ ⎠+
12.1
2V=
:=
Cap
acita
nce:
Co
1D
−(
)
8Lo⋅
Fs2
⋅V
opp
⋅25
010
3−
×Fμ⋅
=:=
RM
S C
urre
nt R
atin
g:Ic
aprm
s1
D−
()
Von
om⋅
23
Lo⋅Fs⋅
0.03
5A=
:=
Cho
ose
a 25
V 5
0uF
capa
cito
r
Pow
er L
oss
Cal
cula
tions
MO
SFE
T Lo
ss C
alcu
latio
ns:
Rds
on13
mΩ⋅
:=n
011
..:=
Load
n
0.01 5 10 20 30 40 50 60 70 80 90 100
:=
Out
put C
urre
nt A
rray
:Io
n
Load
n
100
Pom
ax⋅
Von
om
⎛ ⎜ ⎜ ⎝
⎞ ⎟ ⎟ ⎠:=
Sta
tic L
oss:
Idrm
s nIo
nD
⋅1
Iccm
+⋅
:=
Pmos
1 nIo
nD
⋅1
Iccm
+⋅
()2 R
dson
:=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 61
Sw
itchi
ng L
oss:
ton1
12ns
:=to
ff1
15ns
:=C
oss
700p
F:=
Qg
21nC
:=
Vg
12V
:=Pm
os2 n
Ion
Vin
om⋅
ton1
toff
1+
()
⋅Fs⋅
6:=
Pcos
s1 2
Cos
s⋅
Vin
om2
⋅Fs⋅
0.05
W=
:=Pg
ate
1 2Q
g⋅
Vg
⋅Fs⋅
0.03
2W=
:=
Pmos
tot n
Pmos
1 nPm
os2 n
+Pc
oss
+Pg
ate
+:=
Dio
de L
oss
Cal
cula
tions
Ifav
g nIo
n1
D−
()
⋅:=
From
Dio
de D
atas
heet
:V
f n
0.02
V0.
46V
0.5V
0.58
V0.
61V
0.64
V0.
66V
0.68
V0.
7V0.
71V
0.73
V
:=
Dyn
amic
Res
ista
nce:
Rd
0.62
V0.
4V−
4A0.
5A−
0.06
3Ω=
:=
Pea
k to
pea
k In
duct
or C
urre
ntΔ
ILV
onom
1D
−(
)⋅
LoFs⋅
0.12
A=
:=
Ifrm
s n1
D−
()
3Io
nΔ
IL 2+
⎛ ⎜ ⎝⎞ ⎟ ⎠2
Ion
ΔIL 2
−⎛ ⎜ ⎝
⎞ ⎟ ⎠2+
Ion
ΔIL 2
−⎛ ⎜ ⎝
⎞ ⎟ ⎠Io
nΔ
IL 2+
⎛ ⎜ ⎝⎞ ⎟ ⎠
⋅+
⎡ ⎢ ⎣
⎤ ⎥ ⎦⋅
:=
Pd1 n
Vf n
Ifav
g n⋅
Ifrm
s n(
)2 Rd
+:=
From
Dat
ashe
et:
Vr
Vin
omV
onom
−:=
Ir0.
0001
5A:=
Pd2
VrI
r⋅
1D
−(
)⋅
0.00
1W=
:=
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 62
Ass
ume:
tfr50
0ns
:=V
fp10
V:=
Pd3 n
0.4
Vfp
Vf n
−(
)⋅
tfr⋅If
avg n
⋅Fs⋅
:=
Pdto
t nPd
1 nPd
2+
Pd3 n
+:=
Indu
ctor
Los
s C
alcu
latio
n
ILrm
s nIo
n1
1 3Δ
IL2
Ion
⋅⎛ ⎜ ⎝
⎞ ⎟ ⎠2⋅
+⋅
:=PL
o nIL
rms n
()2
RLo
⋅:=
Cap
acito
r Los
s C
alcu
latio
nA
ssum
e:ES
R15
0mΩ⋅
:=
Icrm
sΔI
L
23
0.03
5A=
:=Pc
Icrm
s2ES
R⋅
:=
Tota
l Los
s C
alcu
latio
n
Ptot
aln
Pmos
tot n
Pdto
t n+
PLo n
+Pc
+:=
Pon
Von
omIo
n⋅
:=
Effi
cien
cy =
=>η
n
Pon
Pon
Ptot
aln
+:=
010
2030
4050
6070
8090
100
0.5
0.54
5
0.59
0.63
5
0.68
0.72
5
0.77
0.81
5
0.86
0.90
5
0.95
Effic
ienc
y of
12V
120
W
Perc
ent L
oad
Efficiency
ηn
Load
n
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 63
Anot
her E
xam
ple
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 64
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 65
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 66
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 67
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 68
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 69
0
R1a {R
top}
+-
+
-
Sbr
eak
S1
Vfb
VV
148
R1
{(10
0/pe
rcen
tload
)*(V
o/10
)}
Vtri
TD =
0
TF =
{5u-
10n}
PW
= 2
0nP
ER
= {1
/100
k}
V1
= 5
TR =
{5u-
10n}
V2
= 0
Vg
Vg
R1b {m
ult*
((ra
tio*R
top)
/(1-r
atio
))}
Dbr
eak
D1
I 0
CO
MP
AR
ATO
R
LIM
IT(1
ME
G*V
(%IN
+, %
IN-)
,5,0
)E
VA
LUE
OU
T+O
UT-
IN+
IN-
{Vre
f}
0
1004 0
C1 50
u 0
Vou
tL1 50
u
12
PARA
MET
ERS:
Vre
f = 2
.5V
o =
12ra
tio =
{Vre
f/Vo}
Rto
p =
10k
mul
t = 0
.992
perc
entlo
ad =
10
Vfb
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 70
Ti
me
0s
0.5m
s 1.
0ms
1.5m
s 2.
0ms
2.5m
s3.
0ms
3.5m
s4.
0ms
4.5m
s 5.
0ms
I(L1)
0A
10A
20A
30A
Indu
ctor
Cur
rent
at M
axim
um L
oad
(10.
000
Am
ps)
V(V
out)
0V
10V
20V
SEL>
>
Out
put V
olta
ge a
t Max
imum
Loa
d
(12.
008
V)
Tim
e
4.69
000m
s4.
6950
0ms
4.70
000m
s4.
7050
0ms
4.71
000m
s4.
7150
0ms
4.68
517m
sI(L
1)
9A10A
11A
Indu
ctor
Cur
rent
Rip
ple
at M
axim
um L
oad
(9.1
136
Amps
)(1
0.88
3 Am
ps)
V(Vo
ut)
11.9
800V
12.0
000V
12.0
200V
11.9
695V
SEL
>>
Out
put V
olta
ge R
ippl
e at
Max
imum
Loa
d
(11.
977
V)
(12.
023
V)
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 71
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 72
Effic
iency
Impr
ovem
ent
•W
ays
to im
prov
e co
nver
ter’s
effi
cien
cy:
–M
OS
FET
•Lo
w R
dson
for H
igh
Dut
y C
ycle
•Lo
w G
ate
Cha
rge
for L
ow D
uty
Cyc
le•
Par
alle
ling
for H
igh
Cur
rent
–S
chot
tky
Dio
de•
Low
forw
ard
drop
•S
hort
reco
very
tim
e–
Indu
ctor
•M
ultip
le p
aral
lel w
indi
ng s
uch
as B
ifilia
r (tw
o w
indi
ngs)
, Trif
iliar
(thr
ee w
indi
ngs)
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 73
Effic
iency
Impr
ovem
ent
–C
apac
itors
•Lo
w E
SR
•P
aral
lelin
g ca
ps (i
ncre
asin
g ca
paci
tanc
e w
hile
re
duci
ng E
SR
s)–
Low
er in
duct
or c
urre
nt ri
pple
•R
educ
e rm
s lo
ss (i
nduc
tor a
nd o
utpu
t cap
acito
r)•
Incr
ease
sw
itchi
ng fr
eque
ncy
or in
duct
ance
–S
witc
hing
loss
and
real
-est
ate
trade
off
–Lo
wer
gat
e dr
ive
volta
ge–
Use
of S
ynch
rono
us M
OS
FET
in p
lace
of
diod
e, e
spec
ially
for l
ow v
olta
ge a
nd h
igh
curr
ent o
utpu
t
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 74
Sync
hron
ous R
ectif
icatio
n•
Rep
lace
s fre
ewhe
elin
g sc
hottk
y w
ith M
OS
FET
•E
spec
ially
ben
efic
ial o
n lo
w d
uty
cycl
e an
d hi
gh c
urre
nt a
pplic
atio
ns•
Due
to re
quire
d de
ad ti
me
and
slow
MO
SFE
T’s
body
dio
de, a
S
chot
tky
is c
onne
cted
acr
oss
the
Syn
chro
nous
MO
SFE
T•
MO
SFE
T +
Scho
ttky
= FE
TKY
com
bo s
uch
as IR
F732
6D2
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 75
Soft-
Switc
hing
•P
reve
nts
hard
-sw
itchi
ng o
r the
ove
rlapp
ing
of s
witc
h’s
volta
ge a
nd
curre
nt d
urin
g tu
rn-o
n an
d tu
rn-o
ff tra
nsiti
ons
–sw
itchi
ng lo
sses
whi
ch is
pro
porti
onal
to s
witc
hing
freq
uenc
y•
Use
of r
eson
ant c
ircui
t to
shap
e sw
itch
volta
ge a
nd/o
r cur
rent
w
avef
orm
s to
inhe
rent
ly g
o to
zer
o at
whi
ch s
witc
hing
tran
sitio
nis
in
itiat
ed
zero
sw
itchi
ng lo
ss
turn
on
turn
off
I onV
off
I onV
off
0
p sw
itchi
ng(t)
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 76
Soft-
Switc
hing
•Q
uasi
-res
onan
t buc
k to
polo
gies
suc
h as
Zer
o-V
olta
ge
and
Zero
Cur
rent
Res
onan
t Sw
itch
Buc
k co
nver
ter
•N
eeds
con
stan
t-on
or c
onst
ant-o
ff co
ntro
llers
suc
h as
U
C18
65 -
UC
1868
, UC
1861
–U
C18
64, M
C34
067
and
MC
3306
7, T
DA
4605
-3, T
DA
4605
-2
turn
on
turn
off
0
I onV
off
I onV
off
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 77
Soft-
Switc
hing
•Ze
ro-C
urre
nt R
eson
ant S
witc
h B
uck
–Tu
rns
switc
h O
FF a
t zer
o cu
rren
t
•Ze
ro-V
olta
ge R
eson
ant S
witc
h B
uck
–Tu
rns
switc
h O
N a
t zer
o vo
ltage
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 78
PWM
Cont
rolle
r•
Cur
rent
Mod
e C
ontro
ller w
ill b
e us
ed d
ue to
man
y of
its
adva
ntag
es–
Eas
y C
ompe
nsat
ion
•W
ith v
olta
ge-m
ode,
the
shar
p ph
ase
drop
afte
r the
filte
r res
onan
t fre
quen
cy
requ
ires
a ty
pe II
I com
pens
ator
to s
tabi
lize
the
syst
em•
Cur
rent
-mod
e co
ntro
l loo
ks li
ke a
sin
gle-
pole
sys
tem
, sin
ce th
e in
duct
or h
as
been
con
trolle
d by
the
curre
nt lo
op•
Impr
oves
the
phas
e m
argi
n, m
akes
the
conv
erte
r muc
h ea
sier
to c
ontro
l•
A ty
pe 2
com
pens
ator
is a
dequ
ate,
gre
atly
sim
plifi
es th
e de
sign
pro
cess
•W
ith v
olta
ge-m
ode
cont
rol,
cros
sove
r has
to b
e w
ell a
bove
the
reso
nant
fre
quen
cy, o
r the
filte
r will
ring.
–
CC
M a
nd D
CM
Ope
ratio
n•
It is
not
pos
sibl
e to
des
ign
a co
mpe
nsat
or w
ith v
olta
ge-m
ode
that
can
pr
ovid
e go
od p
erfo
rman
ce in
bot
h C
CM
and
DC
M•
With
cur
rent
-mod
e, c
ross
ing
the
boun
dary
bet
wee
n th
e tw
o ty
pes
of
oper
atio
n is
not
a p
robl
em•
Hav
ing
optim
al re
spon
se in
bot
h m
odes
is a
maj
or a
dvan
tage
, allo
win
g th
e po
wer
sta
ge to
ope
rate
muc
h m
ore
effic
ient
ly–
Line
Rej
ectio
n•
Clo
sing
the
curr
ent l
oop
give
s a
lot o
f atte
nuat
ion
of in
put n
oise
•Ev
en w
ith o
nly
a m
oder
ate
gain
in th
e vo
ltage
feed
back
loop
, the
atte
nuat
ion
of in
put r
ippl
e is
usu
ally
ade
quat
e w
ith c
urre
nt-m
ode
cont
rol
•W
ith v
olta
ge-m
ode
cont
rol,
far m
ore
gain
(or f
eed
forw
ard)
is n
eede
d in
the
mai
n fe
edba
ck lo
op to
ach
ieve
the
sam
e pe
rform
ance
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 79
PWM
Cont
rolle
r•
For t
he s
ake
of e
xam
ple,
we’
ll us
e U
C18
4x o
r MIC
38H
C4x
fam
ily
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 80
PWM
Cont
rolle
r
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 81
PWM
Cont
rolle
r•
Sel
ectin
g Ti
min
g R
esis
tor a
nd T
imin
g C
apac
itor
–M
axim
um D
uty
Cyc
le a
nd S
witc
hing
Fre
quen
cy h
ave
to b
e de
term
ined
first
–P
erce
nt D
ead
time
wou
ld th
en b
e co
mpu
ted
from
Dm
ax–
Usi
ng %
Dea
d tim
e al
ong
with
Sw
itchi
ng F
requ
ency
, we
can
then
use
pl
ots
prov
ided
in th
e da
ta s
heet
to d
eter
min
e th
e re
quire
d tim
ing
capa
cito
r an
d tim
ing
resi
stor
•E
xam
ple:
Let
’s s
ay th
at D
max
was
cal
cula
ted
to b
e 70
% o
r 0.7
. Add
saf
ety
fact
or to
Dm
ax. S
ay 1
0% s
uch
that
Dm
ax’=
0.8
•Th
e de
ad ti
me
is th
eref
ore
= 10
0% -
80%
= 2
0%•
If sw
itchi
ng fr
eque
ncy
used
is 8
0 kH
z, th
en th
e va
lue
for %
dea
dtim
e al
ong
with
sw
itchi
ng fr
eque
ncy
can
be u
sed
to d
eter
min
e th
e re
quire
d Ti
min
g C
apac
itor
•Th
is is
don
e by
usi
ng th
e pl
ot p
rovi
ded
in th
e da
ta s
heet
.
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 82
PWM
Cont
rolle
r•
From
plo
t, 80
kH
z in
ters
ects
the
20%
dea
d tim
e at
ap
prox
imat
ely
Tim
ing
Cap
acito
r val
ue o
f 10
nF.
•N
ext,
the
timin
g re
sist
or is
foun
d fro
m th
e pl
ot w
hich
is
also
pro
vide
d in
the
data
she
et
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 83
PWM
Cont
rolle
r•
Plo
t sho
ws
that
80k
Hz
inte
rsec
ts th
e tim
ing
capa
cito
r plo
t for
10
nF
at ti
min
g re
sist
ance
app
roxi
mat
ely
equa
ls to
2kΩ
•S
o, in
ord
er to
pro
vide
the
20%
dea
d tim
e at
80
kHz
switc
hing
fre
quen
cy, t
he ti
min
g co
mpo
nent
s ar
e: C
T=
10 n
F an
d R
T=
2 kΩ = 2kΩ
= 10
nF
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 84
PWM
Cont
rolle
r•
Feed
back
Com
pens
atio
n–
As a
sta
rt, ty
pica
lly a
sm
all c
apac
itor i
s pl
aced
on
ZF (s
uch
as 2
200
pF) f
or fe
edba
ck c
ompe
nsat
ion
–O
nce
a pr
otot
ype
is b
uilt,
the
feed
back
com
pens
atio
n w
ill
be in
vest
igat
ed to
giv
e th
e de
sire
d ga
in a
nd p
hase
mar
gin
and
stab
ility
(ove
r wid
e ra
nge
of lo
ad)
–In
volv
es d
ecis
ion
of w
heth
er to
use
type
I, II
, or I
II er
ror
ampl
ifier
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 85
PWM
Cont
rolle
r
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 86
PWM
Cont
rolle
r•
Ste
ps fo
r sel
ectin
g co
mpo
nent
s in
Typ
e 2
–C
hoos
e cr
oss-
over
freq
uenc
y F c
ross
to b
e ar
ound
1/3
of
switc
hing
freq
uenc
y F s
witc
h–
The
requ
ired
pole
freq
uenc
y F p
0th
at y
ield
s th
e de
sire
d cr
osso
ver f
requ
ency
of t
he o
pen
loop
gai
n (w
here
H0
is d
c ga
in
of th
e pl
ant)
211
2p
RCF
π=
–C
alcu
late
cap
acito
r C1
whe
re R
1sh
ould
hav
e be
en s
elec
ted
whe
n se
tting
the
volta
ge d
ivid
er
–C
alcu
late
R2
usin
g th
e pr
evio
usly
cal
cula
ted
C1
and
the
outp
ut
pole
of t
he p
lant
Fp
–C
alcu
late
cap
acito
r C3
whe
re F
esris
the
loca
tion
of th
e E
SR z
ero
0cross
po
FF
H=
11
0
12
p
CRF
π=
31
2esr
CESRF
π=
⋅
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 87
PWM
Cont
rolle
r•
Cur
rent
Sen
sing
Res
isto
r–
Nee
d to
cal
cula
te p
ower
ratin
g of
the
sens
ing
resi
stor
. Thi
s in
volv
es c
alcu
latin
g w
orst
cas
e I rm
s th
roug
h th
e se
nsin
g re
sist
or,
and
then
com
pute
P =
(Irm
s)2*R
sens
e–
A lo
w p
ass
RC
filte
r circ
uit i
s al
so n
eede
d to
elim
inat
e le
adin
gsp
ike
on th
e pu
lse
volta
ge re
sulte
d fro
m c
urre
nt b
eing
sen
sed
–E
nsur
e th
at v
olta
ge o
ut o
f the
filte
r is
less
than
1V
(for
this
co
ntro
ller).
If n
ot, t
hen
redu
ce th
e va
lue
of R
sens
e
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 88
Layo
ut C
onsid
erat
ions
•K
eep
trace
indu
ctan
ce lo
w (p
refe
rabl
y by
redu
cing
leng
th, n
ot
incr
easi
ng w
idth
) for
the
criti
cal p
ath
(sw
itch
and
diod
e pa
ths)
–N
oise
spi
kes
may
app
ear i
n in
put a
nd o
utpu
t, an
d to
the
cont
rolle
r chi
p–
Avo
id u
sing
a c
urre
nt p
robe
(a lo
op o
f wire
) for
dio
de a
nd s
witc
h du
e to
ad
ditio
nal i
nduc
tanc
e it
will
pro
duce
•P
rovi
sion
of g
ood
Inpu
t dec
oupl
ing
sinc
e in
put c
apac
itor i
s in
the
criti
cal p
ath
–B
esid
es th
e us
ual b
ulk
capa
cito
r, al
so p
ut a
sm
all c
eram
ic c
apac
itor a
t th
e su
pply
end
to g
roun
d, a
nd a
noth
er o
ne c
lose
to th
e sw
itch
togr
ound
•P
rovi
sion
of g
ood
deco
uplin
g w
ith a
sm
all c
eram
ic c
apac
itor
betw
een
inpu
t and
gro
und
pins
•Tr
y us
ing
shie
lded
indu
ctor
, and
pos
ition
the
indu
ctor
aw
ay fr
omth
e co
ntro
ller a
nd fe
edba
ck tr
ace
•In
mul
ti-la
yer b
oard
s, d
edic
ate
one
laye
r for
gro
und
•K
eep
the
feed
back
trac
e as
sho
rt as
pos
sibl
e to
min
imiz
e no
ise
pick
up a
nd p
lace
it a
way
from
noi
se s
ourc
es
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 89
Multi
phas
e•
The
tech
niqu
e us
ed m
ainl
y in
ver
y lo
w v
olta
ge a
nd h
igh
pow
er a
pplic
atio
ns s
uch
as p
roce
ssor
s–
Nex
t-gen
erat
ion
netw
orki
ng A
SIC
s an
d pr
oces
sors
requ
ire
mul
tiple
low
er v
olta
ges,
hig
her c
urre
nts,
fast
er d
ynam
ic
resp
onse
, gre
ater
effi
cien
cy a
nd p
ower
man
agem
ent s
olut
ions
th
at re
side
clo
se to
the
load
–To
mee
t the
nee
d of
incr
easi
ng p
ower
den
sity
thro
ugh
high
er
effic
ienc
ies
and
high
er o
pera
ting
frequ
enci
es•
A n
ovel
pow
er a
rchi
tect
ure,
mul
tipha
sing
topo
logi
es, i
s em
ergi
ng to
con
tend
with
tom
orro
w's
pow
er
requ
irem
ents
•H
igh-
dens
ity a
pplic
atio
ns w
ith lo
wer
pow
er le
vels
are
us
ually
man
aged
with
2-p
hase
sol
utio
ns, w
here
as h
ighe
r po
wer
leve
ls c
an re
quire
up
to 4
-pha
se s
olut
ions
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 90
Multi
phas
e•
Mul
tipha
sing
add
ress
5 k
ey p
aram
eter
s in
pow
er c
onve
rsio
n–
Effi
cien
cy: T
he b
est p
ower
effi
cien
cy is
ach
ieve
d by
con
verti
ng a
vo
ltage
in a
sin
gle
stag
e, ra
ther
than
dou
ble
conv
ersi
on.
•Fo
r exa
mpl
e, a
ssum
e yo
u w
ant t
o co
nver
t 48V
to 1
.2V
at
100W
usi
ng a
2-p
hase
forw
ard
conv
erte
r•
In a
2-p
hase
con
vers
ion,
cur
rent
is s
plit
equa
lly in
the
two
phas
es. T
he F
ET
on-lo
sses
are
I2×
R, w
hich
equ
ates
to a
50
% re
duct
ion
in o
n-lo
sses
•Lo
wer
pea
k cu
rrent
s pr
ovid
e lo
wer
turn
-on
and
turn
-off
loss
es, r
esul
ting
in lo
wer
sw
itchi
ng lo
sses
•Lo
wer
turn
-on
and
switc
hing
loss
es p
rovi
de o
vera
ll gr
eate
r ef
ficie
ncy
–In
put/o
utpu
t rip
ple
redu
ctio
n: M
ultip
hasi
ng P
WM
con
trolle
rs
incr
ease
s sw
itchi
ng fr
eque
ncy.
The
resu
lting
freq
uenc
y is
eq
uiva
lent
to th
e P
WM
clo
ck fr
eque
ncy
times
the
num
ber o
f ph
ases
. Hig
her o
pera
ting
frequ
ency
equ
ates
to le
ss in
put/o
utpu
t ca
paci
tanc
e an
d sm
alle
r inp
ut/o
utpu
t ind
ucto
rs
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 91
Multi
phas
e–
Fast
dyn
amic
resp
onse
. Im
prov
ed d
ynam
ic re
spon
se is
th
e re
sult
of s
mal
ler o
utpu
t ind
ucto
rs a
llow
ing
for f
ast
resp
onse
to c
urre
nt c
hang
es c
ombi
ned
with
hig
her
oper
atin
g fre
quen
cy, e
qual
to c
lock
freq
uenc
y tim
es th
e nu
mbe
r of p
hase
s, w
hich
allo
ws
for h
ighe
r cro
ssov
er.
–E
ase
of m
anuf
actu
rabi
lity:
Nex
t-gen
erat
ion
desi
gns
dem
and
smal
ler f
orm
fact
ors
and
auto
mat
ed a
ssem
bly,
es
chew
ing
hand
sol
derin
g of
larg
e tra
nsfo
rmer
s, in
duct
ors
and
capa
cito
rs.
–B
ette
r the
rmal
man
agem
ent:
Ther
mal
man
agem
ent i
s cr
itica
l at t
hese
new
pow
er d
ensi
ties.
The
cha
lleng
e is
ev
en h
ighe
r with
the
emer
genc
e of
mod
ules
ope
ratin
g in
ex
tend
ed te
mpe
ratu
re ra
nge.
With
mul
tipha
sing
te
chni
ques
, you
spr
ead
the
heat
eve
nly
over
the
who
le
conv
erte
r, av
oidi
ng h
ot s
pots
and
impr
ovin
g co
nver
ter
relia
bilit
y
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 92
Multi
phas
e
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 93
Multi
phas
e
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 94
Two-
Phas
e vs.
1 Buc
k
0
L2 200u
12
V5
TD =
{0.5
/50k
}
TF =
10n
PW
= {
Dut
y*(
1/50
k)}
PER
= {
1/50
k}
V1
= 0
TR =
10n
V2
= 1
0
C2 50
u
L3 200u
12
Dbr
eak
D3
V2
TD =
0
TF =
10n
PW
= {(
3.18
5/12
)*(1
/50k
)}P
ER =
{1/
50k}
V1
= 0
TR =
10n
V2
= 1
+-
+
-
Sbre
ak
S1V
R1 2.
5
PA
RA
ME
TE
RS
:D
uty
= {
3.13
5/12
}
R2 2.
5
V3
12D
brea
kD
1
L1 200u
12
V
+-
+
-
Sbre
ak
S2
V112
V4
TD =
0
TF =
10n
PW
= {
Dut
y*(
1/50
k)}
PER
= {
1/50
k}
V1
= 0
TR =
10n
V2
= 1
+-
+
-
Sbre
ak
S3
Dbr
eak
D2
C1 50
u
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 95
Two-
Phas
e vs.
1 Buc
k
Time
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2)
V(L2:2)
0V
1.0V
2.0V
3.0V
4.0V
Output Voltage
2.5 Volts
Just a Buck
Two-Phase Buck
Time
3.6400ms
3.6600ms
3.6800ms
3.7000ms
3.7200ms
3.6203ms
V(R1:2)
V(L2:2)
2.4900V
2.5000V
2.5100V
2.5200V
2.4803V
Output Voltage Ripple
Two-Phase Buck
Just a Buck
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 96
Two-
Phas
e vs.
1 Buc
k
Time
4.6800ms
4.6900ms
4.7000ms
4.7100ms
4.7200ms
4.7300ms
4.7400ms
4.6705ms
4.7500ms
-I(C2)
-I(C1)
-200mA
0A
200mA
Two-phase Buck
Just a Buck
Capacitor Current
Time
4.0000ms
4.0200ms
4.0400ms
4.0600ms
4.0800ms
4.1000ms
3.9886ms
-I(V1)
-I(V3)
0A
0.5A
1.0A
1.5A
Two-Phase
Just a Buck
Input Currents
Prac
tical
Desig
n of B
uck C
onve
rter
PECO
N 20
08, J
ohor
Bah
ru, M
alays
iaTa
ufik
| Pag
e 97
Pow
er E
lect
roni
cs L
ab a
t Cal
Pol
y S
tate
Uni
vers
ity•
6 In
stru
ctio
nal L
ab B
ench
es, 2
Pro
ject
/The
sis
Ben
ches
•Fo
r fur
ther
info
rmat
ion,
con
tact
Pow
er E
lect
roni
cs L
ab C
oord
inat
or, D
r. Ta
ufik
at t
aufik
@ca
lpol
y.ed
u
