FSDH321_04 Datasheet, PDF (14/20 Pages) Fairchild Semiconductor – Green Mode Fairchild Power Switch

FSDH321, FSDL321
Typical application circuit
1. PC Auxiliary Power Circuit (10W Output Power)
140~375
VDC
INPUT
R102
100kΩ
1W
C101
10nF
630V
T1
EE1625
D201
SB360
1
10
C201
1000uF
16V
2
7
L201
10uH
C203
470uF
16V
R101
680kΩ
1W
5
D101
UF 4007
M Vcc
D102
1N4937
3
R103
10Ω ₄
IC101 Vstr
FSDx321
3
Vfb
Drain 6,7,8
Vcc ²
D103
1N4937
C104
22nF
GND
1
C103
10uF
50V
C102
47uF
50V _R104
10Ω
5
6
PC301
H11A817A
R202
330Ω
R201
1kΩ
C202
100nF
R203
2kΩ
C301
2.2nF
IC201
KA431
R204
2kΩ
5V
(+/-5%)
2A
10W PC Auxiliary Power Circuit
10W PC Auxiliary Power, 150~375VDC Input Power
supply:
It shows a auxiliary power for PC. Efficiency at 10W, 150/
375VDC is ≥70%.
The PC application has the standard of standby power con-
sumption, under 1W at the output load, 0.5W and height
input voltage, 230VAC. For this the FSDH321 also has the
burst operating function like the any other green mode FPS
like FSDM0265RN or FSDM0365RN and so on. This skill
reduces the MOSFET switching numbers and power MOS-
FET switching loss. This design takes advantage of self pro-
tection without external components and high switching
frequency, 100kHz. The frequency makes using a small size
transformer core possible. The EE16 or EE1625 can be used
for 10W application.
This is achieved by preventing the green FPS from switching
when the input voltage goes below a level needed to main-
tain output regulation, and keeping it off until the input volt-
age goes above the under-voltage threshold, when the AC is
turned on again. For example with the resistor, R101,
680kΩ, the threshold voltage is around 150VAC(210VDC)
at the room temperature.
Leakage inductance clamping is provided by R102 and
C101, keeping the DRAIN voltage below 650 V under all
conditions. And R102 dissipates power to prevent rising of
DRAIN Voltage caused by leakage inductance. The fre-
quency modulation feature of FSDH321 allows the circuit
shown to meet CISPR2AB with simple EMI filtering. The
secondary is rectified and smoothed by D201. Similarly
D102 and D103 are also rectifiers for main power control IC
and FSDH321 respectively. The 5V output voltage require
two capacitors in parallel to meet the ripple current require-
ment. Switching noise filtering is provided by L201. The
output is regulated by the reference (TL431) voltage in sec-
ondary. It is sensed via R203 and R204. Resistor R201 pro-
vides bias for TL431 and R202 sets the overall DC gain.
R2012, C202 and R203 provide loop compensation.
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