非隔离式直流直流转换器介绍

vripple = 300mV = 2 A × Resr ⇒ Resr = 150mΩ
∴C = 433μF ⇒ C = 470μF / 63V
Design Example
Step 4—Choice of the power switch.
I I
DS ,max DS ,max
≥ 1.2 × Iin = 1.2 × (1
Noninverting buck-boost converter
Reversal of output voltage polarity
Reduction of number of switches inverting buck-boost
Buck-Boost Converter
A. Continuous-Conduction Mode (CCM)
A. Continuous-Conduction Mode (CCM)
ΔVo
=
ΔQ C
=
IO DTs C
=
VO DTs RC
⇒
ΔVo Vo
=
DTs RC
Boost Converter
B. Boundary Between CCM and DCM
I LB
=
1 2
iL,
peak
=
tonVd 2L
=
DTsVd 2L
=
TsVo 2L
D(1 −
D)
I oB
=
(1− D)Id
=
(1 − D)ILB
=
TsVo 2L
D(1− D)2
I LB,max
=
TsVo 8L
(when D=0.5)
∴ I LB = 4D(1 − D)I LB,max
I oB ,max
=
2 TsVo 27 L
=
0.074
TsVo L
(when D=0.5)
∴ IoB
=
27 4
D(1
−
D)2
I
oB,max
Boost Converter
C. Discontinuous-Conduction Mode (DCM)
Vd DTs + (Vd −Vo )Δ1Ts = 0
⇒
Vo Vd
= Δ1 + D Δ1
IL
= iL,peak
D + Δ1 2
=
Vd L
DTs
D + Δ1 2
VD,max > 1.2 ×VO = 1.2 × 48 = 57.6V Thus, we choose S3L56 as the power diode
Cascade connection of converters
Example: buck cascaded by boost
Buck cascaded by boost simplification of internal filter
Vin=40V~60V (input voltage); Vo=12V (output voltage); Po,max=100W (maximum output power); fs=100kHz (switching frequency). vripple=100mV (output voltage ripple)
⇒
D
=
VO Vd
IO I OB ,max
Discussion: cascade connections Rotation of three-terminal cell
Rotation of a dual three-terminal network
Cuk Converter
Cuk Converter Cuk Converter
=
(1 − D)Ts2 8LC
Buck Converter
B. Boundary Between CCM and DCM
I LB
=
1 2
iL
,
peak
=
ton 2L
(Vd
− Vo ) =
DTs 2L
(Vd
− Vo ) =
I OB
I LB
=
TsVd 2L
D(1 −
D)
I LB,max
=
TsVd 8L
(when D=0.5)
⇒
Vo Vg
=
ton Ts
=D
Buck Converter
A. Continuous-Conduction Mode (CCM)
ΔVo
=
ΔQ C
=
1 C
•
1 2
•
ΔI L 2
•
Ts 2
ΔI L
=
Vg
− Vo L
DTs
=
Vo L
(1 −
D)Ts
∴ ΔVo
=
Ts 8C
•
Vo L
(1 −
D)Ts
⇒
ΔVo Vo
× Toff ,max
L
≥
12
+ 0.7 2
× 8μ
=
50.8μH
Step 3—Choice of the output filter capacitor.
vripple = ΔIO × Rset
and
C
= 65×10−6
ΔI O vripple
=
65 ×10 −6 Rset
∴50mV = 0.2ΔIO × R ⇒ 50mV = 0.2(2) × R ⇒ R
I
LB
∴ IOB
=
TsVO 2L
(1− D)2
I OB ,max
=
TsVO 2L
= I LB,max
∴ I LB = I LB,max (1 − D)
∴ IOB = IOB max (1 − D)2
Buck-Boost Converter
C. Discontinuous-Conduction Mode (CCM)
≥
1.2
×
(1
2
− 0.5)
=
4.8
IO − Dmax
A
)
VDS,max > 1.2 ×VO = 1.2 × 48 = 57.6V
Thus, we choose IRF540 as the power switch
Step 5—Choice of the power diode.
ID,max > 1.2 × IO = 1.2 × 2 = 2.4 A
Step 2—Calculation of the output filter inductor.
Dmax
=
VO VIN ,min
=
12 40
= 0.3
and
Dmin
=
VO VIN ,max
=
12 60
= 0.2
( ) Toff ,max = TS × 1 − Dmin = 8μs
( ) L
≥
VL off ΔIO
= 120mΩ
Design Example
∴C
=
65 × 10−6
1 120m
=
541μF
Step 4—Choice of the power switch.
IDS,max ≥ 1.2 × IO = 1.2 × 8 = 9.6A VDS,max > 1.2 ×VO = 1.2 × 60 = 72V
i(0)
=
1 L
tv
0
L
dt
∫ ⇒ i(Ts ) − i(0) =
1 L
Ts 0
v
L
dt
In steady state i(Ts ) = i(0)
∫ ∫ ∫ ∴
Ts 0
v L dt
=
0
⇒
(V ton
0
g
− Vo )dt
+
Ts ton
(
−Vo
)dt
=
0
⇒ (Vg − Vo )ton + (−Vo )(Ts − ton ) = 0
Vd DTs + (−Vo )Δ1Ts
=0
⇒
Vo Vd
D =
Δ1
IL
=
iL,peak (D + Δ1)
=
Vd 2L
DTs (D + Δ1)
⇒
IO
+ Id
=
Vd Ts 2L
D(D + Δ1)
=
TsVo 2L
Δ1(D + Δ1)
⇒
IO
+
D Δ1
IO
=
I OB ,max
Vd VO
D(D +
D Vd VO
)
Vd DTs + (−Vo )(1 − D)Ts = 0
⇒
Vo Vd
=
1
D −D
Buck-Boost Converter
A. Continuous-Conduction Mode (CCM)
ΔVo
=
ΔQ C
=
IO DTs C
=
VO DTs RC
⇒
ΔVo Vo
=
DTs RC
Buck-Boost Converter
B. Boundary Between CCM and DCM
I LB
=
1 2
iL,
peak
=
TsVd 2L
D
Q IO = IL − Id
I LB IOB ⇒
=
TsVo 2L
(1 −
D)
= I LB − Id = I LB −
1 1− D
IOB
=
I LB
⇒
D 1− D IOB =
IOB (1 −
D
)
非隔離式DC/DC 轉換器介紹 Buck Converter
Buck Converter
A. Continuous-Conduction Mode (CCM)
Buck Converter
A. Continuous-Conduction Mode (CCM)
∫ ∫ vL
=
L
di dt
⇒
di i(Ts )
Step 2—Calculation of the output filter inductor.
( ) L
≥
VO TS
Dmin 2
1− I OB
Dmin
2
L ≥ 48 × 8.7 μ × 0.17 × 0.68 = 12 μH 2×2
Step 3—Choice of the output filter capacitor.
∴ I LB = 4I LB max D(1 − D)
Buck Converter
C. Discontinuous-Conduction Mode (DCM)
(Vg − Vo )DTs + (−Vo )Δ1Ts = 0
⇒
Vo Vd
=
D D + Δ1
Io
=
D
+ 2
Δ1
iL, peak
=
(Vd
− L
Vo
SEPIC Converter ZETA Converter
Δ1
= =
Vd Ts 2L
D(
IL
Ts 2L
DVo
D=+24Δ71I)OI=BL,m2TaxLsDD=Δ1V24Δo71ΔI+O1BD,maIxOD
=
( VO Vd
)IO
27 4
I OB ,max
D
∴
VO Vd
=
Δ1 + D Δ1
= 1+
D (VO /Vd )IO
∴
(VO Vd
− 1)
=
D2 (27 / 4)IOB,max D
TL494
Pulse-Width-Modulation Control Circuits
Functional block diagram TL494
TL494 UC3842
Functional block diagram UC3842
UC3842 UC3842
UC3842 UC3842
UC3842 UC3842
)
DTs
D + Δ1 2
=
VoTs 2L
(D − Δ1)Δ1
=
Vd Ts 2L
DΔ1
=
4I LB,max DΔ1
⇒
Δ1
=
Io 4I LB,max D
⇒
Vo Vd
=
D
+
D Io
4I LB max D
=
D2ห้องสมุดไป่ตู้
D2
+
Io 4I LB max
Design Example
Step 1—Input and output data specification.
4 27
(VVOd
)(
I
IO
OB
)
⇒
D
=
⎡ ⎢ ⎣
4 27
(VO Vd
)(VO Vd
1
−
1)(
IO I OB ,max
)⎥⎤ ⎦
2
Design Example
Step 1—Input and output data specification.
Vin=24V~40V (input voltage); Vo=48V (output voltage); Po,max=100W (maximum output power); fs=115kHz (switching frequency). vripple=300mV (output voltage ripple)
Inversion of source and load Boost Converter
Boost Converter
A. Continuous-Conduction Mode (CCM)
Vd ton + (Vd −Vo )toff = 0
⇒
Vo Vd
=
Ts toff
=
1
1 −D
Boost Converter
Thus, we choose IRF540 as the power switch
Step 5—Choice of the power diode.
ID,max > 1.2 × IO = 1.2 × 8 = 9.6A VD,max > 1.2 ×VO = 1.2 × 60 = 72V Thus, we choose S30L60 as the power diode