AN-8027 データシートの表示（PDF） - Fairchild Semiconductor
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AN-8027 Datasheet PDF : 17 Pages
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AN-8027
Design Considerations
In this section, a design procedure is presented using the
schematic in Figure 11 as reference. A 300W PC power
supply application with universal input range is selected as
a design example. The design specifications are
summarized in 0. The two-switch forward converter is used
for DC/DC converter stage.
Design Specifications
Rated Voltage of Output 1
Rated Current of Output 1
Rated Voltage of Output 2
Rated Current of Output 2
Rated Voltage of Output 3
Rated Current of Output 3
Rated Voltage of Output 4
Rated Current of Output 4
Rated Output Power
Line Voltage Range
Line Frequency
Brownout Protection Line Voltage
Overall Stage Efficiency
VOUT1 = 5V
IOUT1 = 9A
Vout2 = 12V
IOUT2 = 16.5A
VOUT3 = -12V
IOUT3 = 0.8A
VOUT4 = 3.3V
IOUT4 = 13.5A
PO = 300W
85~264VAC
50Hz
72VAC
η = 0.82
PWM Stage Efficiency
Hold-up Time
Minimum PFC Output Voltage
Nominal PFC output voltage
PFC Output Voltage Ripple
PFC Inductor Ripple Current
AC Input Voltage Frequency
Switching Frequency
Total Harmonic Distortion
Magnetic Flux Density
Current Density
PWM Maximum Duty Cycle
5V Output Current Ripple
12V Output Current Ripple
ηPWM = 0.86
tHLD = 20ms
310V
VO_PFC = 387V
12VPP
dI = 40%
fline = 50 ~ 60Hz
fS = 65KHz
α = 4%
ΔB = 0.27T
Dcma = 400C-m/A
Dmax = 0.35
ILo1 = 44%
ILo2 = 10%
F1
AC
Input
CIF1
L BOOST
DBOOST
Drv
RCS1
CBOOST
Q1
R RAMP
D1 D2
VBOUT
R FB1
Drv
Q2
DR1
Drv
Q3 DR2
DR1
L1
1
DF1
L1
2
Vo1
CO11
CO12
L22
DR2
L2
1
DF2 CO21
Vo2
CO22
CIC2
RLF2
RCS2
RRMS1
RLF1
R IAC
RT
CRMS1
RRMS2
RB
CRMS2 RRMS3
CLF1 CSS
CT
RIC
CIC1
IEA
IAC
ISENSE
VRMS
SS
VEA
FBPFC
VREF
VD
D
OPFC
FBPWM
OPWM
RT/CT
GND
RAMP
ILIMIT
FAN480X
CRAMP
CB
VD
D
RVC
CVC1
CVC2
CFB
CLF2 CDD CREF
RFB2
Figure 11. Reference Circuit for Design Example
RBIAS
Vo3
Vo4
RD
Vo1
CF RF
ROS1
ROS2 Vo2
ROS3
© 2009 Fairchild Semiconductor Corporation
Rev. 1.0.0 • 8/26/09
5
www.fairchildsemi.com
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