RD8 查看數據表（PDF） - Power Integrations, Inc
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RD8 Datasheet PDF : 12 Pages
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RD8
L1
5 mH
D3
D1
1N4005 1N4005
R1
2.2 Ω
R2
4.7 kΩ
85-265 Fusible
VAC
C1
4.7 µF
400 V
C2
4.7 µF
400 V
D4
D2
1N4005 1N4005
D5
T1 11DQ06
3
9
C6
330 µF
16 V
4
6
L2
Bead
C7
100 µF
25 V
R4
1.5 kΩ
1/2 W
TinySwitch
D
U1
EN
TNY254P BP
U2
S
LTV817
VR1
1N5237B
C3
68 pF
C4
0.1 µF
+9V
RTN
Figure 2. Schematic Diagram of the 3 W RD8 Power Supply.
C5
2.2 nF
Y1 Safety
PI-2250-090398
R1 D1
C1
T1
D5
L D3
C2
D2
L1
D4
N
U1
C4
R4
C3
U2
C6
L2
C5 Jmp 1
+
C7
VR1 G
COMPONENT SIDE SHOWN*
* Shown 1.5 X actual size PI-2254-091597
Figure 3. Component Legend for the RD8.
General Circuit Description
The RD8 is a low-cost flyback switching power supply using
the TNY254P integrated circuit. The circuit shown in Figure 2
details a 9 V, 3 W power supply that operates from 85 to
265 VAC input voltage, suitable for replacing conventional
linear supplies in cost-sensitive applications such as AC wall
adapters.
AC power is rectified and filtered by D1-4, C1, and C2 to create
the high voltage DC bus applied to the primary winding of T1.
R4 and C3 clamp the primary leakage spike and also reduce
EMI. At this power level, a simple RC network is sufficient for
snubbing leakage spikes. Because of the relatively low switching
frequency of TinySwitch (44 kHz), and its ON/OFF control
method, the additional capacitive loading of the RC snubber
network has a much smaller effect on efficiency than for
conventional PWM switchers running at higher switching
frequencies. Since TinySwitch runs in current limit mode at all
times regardless of output load, the worst case leakage spike
2C
3/99
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